<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2023 Workiva-->
<!--r:41467125-a062-4509-80eb-f626565d3054,g:da5a1d1e-7b71-43fa-a7ad-2abe773088ca-->
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:smsi="http://www.smithmicro.com/20221231" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2020-01-21" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://www.smithmicro.com/20221231">
  <xs:import namespace="http://fasb.org/srt/2022" schemaLocation="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd"/>
  <xs:import namespace="http://fasb.org/us-gaap-sup/2022q3" schemaLocation="https://xbrl.fasb.org/us-gaap/2022q3/us-gaap-sup-2022q3.xsd"/>
  <xs:import namespace="http://fasb.org/us-gaap/2022" schemaLocation="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd"/>
  <xs:import namespace="http://www.w3.org/1999/xlink" schemaLocation="http://www.xbrl.org/2003/xlink-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/dtr/type/2020-01-21" schemaLocation="https://www.xbrl.org/dtr/type/2020-01-21/types.xsd"/>
  <xs:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/dei/2022" schemaLocation="https://xbrl.sec.gov/dei/2022/dei-2022.xsd"/>
  <xs:annotation>
    <xs:appinfo>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="smsi-20221231_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="smsi-20221231_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="smsi-20221231_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="smsi-20221231_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:type="simple"/>
      <link:roleType id="CoverPage" roleURI="http://www.smithmicro.com/role/CoverPage">
        <link:definition>0000001 - Document - Cover Page</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="AuditInformation" roleURI="http://www.smithmicro.com/role/AuditInformation">
        <link:definition>0000002 - Document - Audit Information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConsolidatedBalanceSheets" roleURI="http://www.smithmicro.com/role/ConsolidatedBalanceSheets">
        <link:definition>0000003 - Statement - Consolidated Balance Sheets</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConsolidatedBalanceSheetsParenthetical" roleURI="http://www.smithmicro.com/role/ConsolidatedBalanceSheetsParenthetical">
        <link:definition>0000004 - Statement - Consolidated Balance Sheets (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConsolidatedStatementsofOperations" roleURI="http://www.smithmicro.com/role/ConsolidatedStatementsofOperations">
        <link:definition>0000005 - Statement - Consolidated Statements of Operations</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConsolidatedStatementsofStockholdersEquity" roleURI="http://www.smithmicro.com/role/ConsolidatedStatementsofStockholdersEquity">
        <link:definition>0000006 - Statement - Consolidated Statements of Stockholders' Equity</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConsolidatedStatementsofCashFlows" roleURI="http://www.smithmicro.com/role/ConsolidatedStatementsofCashFlows">
        <link:definition>0000007 - Statement - Consolidated Statements of Cash Flows</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="OrganizationBasisofPresentationandSummaryofSignificantAccountingPolicies" roleURI="http://www.smithmicro.com/role/OrganizationBasisofPresentationandSummaryofSignificantAccountingPolicies">
        <link:definition>0000008 - Disclosure - Organization, Basis of Presentation and Summary of Significant Accounting Policies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Acquisitions" roleURI="http://www.smithmicro.com/role/Acquisitions">
        <link:definition>0000009 - Disclosure - Acquisitions</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EquipmentandImprovements" roleURI="http://www.smithmicro.com/role/EquipmentandImprovements">
        <link:definition>0000010 - Disclosure - Equipment and Improvements</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssets" roleURI="http://www.smithmicro.com/role/GoodwillandIntangibleAssets">
        <link:definition>0000011 - Disclosure - Goodwill and Intangible Assets</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DebtandWarrantsTransactions" roleURI="http://www.smithmicro.com/role/DebtandWarrantsTransactions">
        <link:definition>0000012 - Disclosure - Debt and Warrants Transactions</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueofFinancialInstruments" roleURI="http://www.smithmicro.com/role/FairValueofFinancialInstruments">
        <link:definition>0000013 - Disclosure - Fair Value of Financial Instruments</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EquityTransactions" roleURI="http://www.smithmicro.com/role/EquityTransactions">
        <link:definition>0000014 - Disclosure - Equity Transactions</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxes" roleURI="http://www.smithmicro.com/role/IncomeTaxes">
        <link:definition>0000015 - Disclosure - Income Taxes</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EarningsPerShare" roleURI="http://www.smithmicro.com/role/EarningsPerShare">
        <link:definition>0000016 - Disclosure - Earnings Per Share</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlans" roleURI="http://www.smithmicro.com/role/EmployeeBenefitPlans">
        <link:definition>0000017 - Disclosure - Employee Benefit Plans</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensation" roleURI="http://www.smithmicro.com/role/StockBasedCompensation">
        <link:definition>0000018 - Disclosure - Stock-Based Compensation</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Revenues" roleURI="http://www.smithmicro.com/role/Revenues">
        <link:definition>0000019 - Disclosure - Revenues</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CommitmentsandContingencies" roleURI="http://www.smithmicro.com/role/CommitmentsandContingencies">
        <link:definition>0000020 - Disclosure - Commitments and Contingencies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Leases" roleURI="http://www.smithmicro.com/role/Leases">
        <link:definition>0000021 - Disclosure - Leases</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SegmentConcentrationandGeographicalInformation" roleURI="http://www.smithmicro.com/role/SegmentConcentrationandGeographicalInformation">
        <link:definition>0000022 - Disclosure - Segment, Concentration and Geographical Information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SubsequentEvents" roleURI="http://www.smithmicro.com/role/SubsequentEvents">
        <link:definition>0000023 - Disclosure - Subsequent Events</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="OrganizationBasisofPresentationandSummaryofSignificantAccountingPoliciesPolicies" roleURI="http://www.smithmicro.com/role/OrganizationBasisofPresentationandSummaryofSignificantAccountingPoliciesPolicies">
        <link:definition>0000024 - Disclosure - Organization, Basis of Presentation and Summary of Significant Accounting Policies (Policies)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="AcquisitionsTables" roleURI="http://www.smithmicro.com/role/AcquisitionsTables">
        <link:definition>0000025 - Disclosure - Acquisitions (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EquipmentandImprovementsTables" roleURI="http://www.smithmicro.com/role/EquipmentandImprovementsTables">
        <link:definition>0000026 - Disclosure - Equipment and Improvements (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssetsTables" roleURI="http://www.smithmicro.com/role/GoodwillandIntangibleAssetsTables">
        <link:definition>0000027 - Disclosure - Goodwill and Intangible Assets (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DebtandWarrantsTransactionsTables" roleURI="http://www.smithmicro.com/role/DebtandWarrantsTransactionsTables">
        <link:definition>0000028 - Disclosure - Debt and Warrants Transactions (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueofFinancialInstrumentsTables" roleURI="http://www.smithmicro.com/role/FairValueofFinancialInstrumentsTables">
        <link:definition>0000029 - Disclosure - Fair Value of Financial Instruments (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxesTables" roleURI="http://www.smithmicro.com/role/IncomeTaxesTables">
        <link:definition>0000030 - Disclosure - Income Taxes (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EarningsPerShareTables" roleURI="http://www.smithmicro.com/role/EarningsPerShareTables">
        <link:definition>0000031 - Disclosure - Earnings Per Share (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensationTables" roleURI="http://www.smithmicro.com/role/StockBasedCompensationTables">
        <link:definition>0000032 - Disclosure - Stock-Based Compensation (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenuesTables" roleURI="http://www.smithmicro.com/role/RevenuesTables">
        <link:definition>0000033 - Disclosure - Revenues (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesTables" roleURI="http://www.smithmicro.com/role/LeasesTables">
        <link:definition>0000034 - Disclosure - Leases (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SegmentConcentrationandGeographicalInformationTables" roleURI="http://www.smithmicro.com/role/SegmentConcentrationandGeographicalInformationTables">
        <link:definition>0000035 - Disclosure - Segment, Concentration and Geographical Information (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="OrganizationBasisofPresentationandSummaryofSignificantAccountingPoliciesAdditionalInformationDetail" roleURI="http://www.smithmicro.com/role/OrganizationBasisofPresentationandSummaryofSignificantAccountingPoliciesAdditionalInformationDetail">
        <link:definition>0000036 - Disclosure - Organization, Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="AcquisitionsAdditionalInformationDetail" roleURI="http://www.smithmicro.com/role/AcquisitionsAdditionalInformationDetail">
        <link:definition>0000037 - Disclosure - Acquisitions - Additional Information (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="AcquisitionsSummaryofConsiderationPaidforAcquisitionsDetail" roleURI="http://www.smithmicro.com/role/AcquisitionsSummaryofConsiderationPaidforAcquisitionsDetail">
        <link:definition>0000038 - Disclosure - Acquisitions - Summary of Consideration Paid for Acquisitions (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="AcquisitionsSummaryofAllocationofPurchasePriceDetail" roleURI="http://www.smithmicro.com/role/AcquisitionsSummaryofAllocationofPurchasePriceDetail">
        <link:definition>0000039 - Disclosure - Acquisitions - Summary of Allocation of Purchase Price (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EquipmentandImprovementsSummaryofEquipmentandImprovementsDetail" roleURI="http://www.smithmicro.com/role/EquipmentandImprovementsSummaryofEquipmentandImprovementsDetail">
        <link:definition>0000040 - Disclosure - Equipment and Improvements - Summary of Equipment and Improvements (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EquipmentandImprovementsAdditionalInformationDetail" roleURI="http://www.smithmicro.com/role/EquipmentandImprovementsAdditionalInformationDetail">
        <link:definition>0000041 - Disclosure - Equipment and Improvements - Additional Information (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssetsScheduleofAcquiredIntangibleAssetsbyMajorAssetClassDetail" roleURI="http://www.smithmicro.com/role/GoodwillandIntangibleAssetsScheduleofAcquiredIntangibleAssetsbyMajorAssetClassDetail">
        <link:definition>0000042 - Disclosure - Goodwill and Intangible Assets - Schedule of Acquired Intangible Assets by Major Asset Class (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssetsAdditionalInformationDetail" roleURI="http://www.smithmicro.com/role/GoodwillandIntangibleAssetsAdditionalInformationDetail">
        <link:definition>0000043 - Disclosure - Goodwill and Intangible Assets - Additional Information (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssetsFutureAmortizationExpenseRelatedtoIntangibleAssetsDetail" roleURI="http://www.smithmicro.com/role/GoodwillandIntangibleAssetsFutureAmortizationExpenseRelatedtoIntangibleAssetsDetail">
        <link:definition>0000044 - Disclosure - Goodwill and Intangible Assets - Future Amortization Expense Related to Intangible Assets (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DebtandWarrantsTransactionsAdditionalInformationDetails" roleURI="http://www.smithmicro.com/role/DebtandWarrantsTransactionsAdditionalInformationDetails">
        <link:definition>0000045 - Disclosure - Debt and Warrants Transactions - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DebtandWarrantsTransactionsAssumptionsDetails" roleURI="http://www.smithmicro.com/role/DebtandWarrantsTransactionsAssumptionsDetails">
        <link:definition>0000046 - Disclosure - Debt and Warrants Transactions - Assumptions (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DebtandWarrantsTransactionsBalanceoftheNotesDetails" roleURI="http://www.smithmicro.com/role/DebtandWarrantsTransactionsBalanceoftheNotesDetails">
        <link:definition>0000047 - Disclosure - Debt and Warrants Transactions - Balance of the Notes (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DebtandWarrantsTransactionsBalanceoftheNotesDetails_1" roleURI="http://www.smithmicro.com/role/DebtandWarrantsTransactionsBalanceoftheNotesDetails_1">
        <link:definition>0000047 - Disclosure - Debt and Warrants Transactions - Balance of the Notes (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueofFinancialInstrumentsLiabilitiesMeasuredatFairValueonaRecurringBasisDetails" roleURI="http://www.smithmicro.com/role/FairValueofFinancialInstrumentsLiabilitiesMeasuredatFairValueonaRecurringBasisDetails">
        <link:definition>0000048 - Disclosure - Fair Value of Financial Instruments - Liabilities Measured at Fair Value on a Recurring Basis (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueofFinancialInstrumentsRollforwardDetails" roleURI="http://www.smithmicro.com/role/FairValueofFinancialInstrumentsRollforwardDetails">
        <link:definition>0000049 - Disclosure - Fair Value of Financial Instruments - Rollforward (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EquityTransactionsAdditionalInformationDetail" roleURI="http://www.smithmicro.com/role/EquityTransactionsAdditionalInformationDetail">
        <link:definition>0000050 - Disclosure - Equity Transactions - Additional Information (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxesScheduleofLossIncomebeforeProvisionforIncomeTaxesDetail" roleURI="http://www.smithmicro.com/role/IncomeTaxesScheduleofLossIncomebeforeProvisionforIncomeTaxesDetail">
        <link:definition>0000051 - Disclosure - Income Taxes - Schedule of (Loss) Income before Provision for Income Taxes (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxesSummaryofIncomeTaxExpenseBenefitDetail" roleURI="http://www.smithmicro.com/role/IncomeTaxesSummaryofIncomeTaxExpenseBenefitDetail">
        <link:definition>0000052 - Disclosure - Income Taxes - Summary of Income Tax Expense (Benefit) (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxesFederalStatutoryRatetoLossBeforeIncomeTaxesDetail" roleURI="http://www.smithmicro.com/role/IncomeTaxesFederalStatutoryRatetoLossBeforeIncomeTaxesDetail">
        <link:definition>0000053 - Disclosure - Income Taxes - Federal Statutory Rate to Loss Before Income Taxes (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxesComponentsofDeferredTaxAssetsandLiabilitiesDetail" roleURI="http://www.smithmicro.com/role/IncomeTaxesComponentsofDeferredTaxAssetsandLiabilitiesDetail">
        <link:definition>0000054 - Disclosure - Income Taxes - Components of Deferred Tax Assets and Liabilities (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxesAdditionalInformationDetail" roleURI="http://www.smithmicro.com/role/IncomeTaxesAdditionalInformationDetail">
        <link:definition>0000055 - Disclosure - Income Taxes - Additional Information (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxesGrossUnrecognizedTaxBenefitsChangesinBalancesDetail" roleURI="http://www.smithmicro.com/role/IncomeTaxesGrossUnrecognizedTaxBenefitsChangesinBalancesDetail">
        <link:definition>0000056 - Disclosure - Income Taxes - Gross Unrecognized Tax Benefits Changes in Balances (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EarningsPerShareDetailsofBasicandDilutedEarningsPerShareDetail" roleURI="http://www.smithmicro.com/role/EarningsPerShareDetailsofBasicandDilutedEarningsPerShareDetail">
        <link:definition>0000057 - Disclosure - Earnings Per Share - Details of Basic and Diluted Earnings Per Share (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EmployeeBenefitPlansAdditionalInformationDetail" roleURI="http://www.smithmicro.com/role/EmployeeBenefitPlansAdditionalInformationDetail">
        <link:definition>0000058 - Disclosure - Employee Benefit Plans - Additional Information (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensationAdditionalInformationDetail" roleURI="http://www.smithmicro.com/role/StockBasedCompensationAdditionalInformationDetail">
        <link:definition>0000059 - Disclosure - Stock-Based Compensation - Additional Information (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensationNonCashStockBasedCompensationExpensesDetail" roleURI="http://www.smithmicro.com/role/StockBasedCompensationNonCashStockBasedCompensationExpensesDetail">
        <link:definition>0000060 - Disclosure - Stock-Based Compensation - Non-Cash Stock-Based Compensation Expenses (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensationAssumptionsUsedtoComputeShareBasedCompensationCostsforStockOptionsGrantedDetail" roleURI="http://www.smithmicro.com/role/StockBasedCompensationAssumptionsUsedtoComputeShareBasedCompensationCostsforStockOptionsGrantedDetail">
        <link:definition>0000061 - Disclosure - Stock-Based Compensation - Assumptions Used to Compute Share-Based Compensation Costs for Stock Options Granted (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensationSummaryofOutstandingStockOptionsandRelatedActivityDetail" roleURI="http://www.smithmicro.com/role/StockBasedCompensationSummaryofOutstandingStockOptionsandRelatedActivityDetail">
        <link:definition>0000062 - Disclosure - Stock-Based Compensation - Summary of Outstanding Stock Options and Related Activity (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensationAssumptionsUsedEstimateFairValueofEmployeeStockPurchasePlansDetail" roleURI="http://www.smithmicro.com/role/StockBasedCompensationAssumptionsUsedEstimateFairValueofEmployeeStockPurchasePlansDetail">
        <link:definition>0000063 - Disclosure - Stock-Based Compensation - Assumptions Used Estimate Fair Value of Employee Stock Purchase Plans (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensationSummaryofOutstandingRestrictedStockAwardsandRelatedActivityDetail" roleURI="http://www.smithmicro.com/role/StockBasedCompensationSummaryofOutstandingRestrictedStockAwardsandRelatedActivityDetail">
        <link:definition>0000064 - Disclosure - Stock-Based Compensation - Summary of Outstanding Restricted Stock Awards and Related Activity (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenuesAdditionalInformationDetail" roleURI="http://www.smithmicro.com/role/RevenuesAdditionalInformationDetail">
        <link:definition>0000065 - Disclosure - Revenues - Additional Information (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenuesScheduleofRevenuesonDisaggregatedBasisDetail" roleURI="http://www.smithmicro.com/role/RevenuesScheduleofRevenuesonDisaggregatedBasisDetail">
        <link:definition>0000066 - Disclosure - Revenues - Schedule of Revenues on Disaggregated Basis (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesSummaryofOperatingLeaseCostDetail" roleURI="http://www.smithmicro.com/role/LeasesSummaryofOperatingLeaseCostDetail">
        <link:definition>0000067 - Disclosure - Leases - Summary of Operating Lease Cost (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesSummaryofOperatingLeaseAssetsandLiabilitiesDetail" roleURI="http://www.smithmicro.com/role/LeasesSummaryofOperatingLeaseAssetsandLiabilitiesDetail">
        <link:definition>0000068 - Disclosure - Leases - Summary of Operating Lease Assets and Liabilities (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesSummaryofMaturityofOperatingLeaseLiabilitiesDetail" roleURI="http://www.smithmicro.com/role/LeasesSummaryofMaturityofOperatingLeaseLiabilitiesDetail">
        <link:definition>0000069 - Disclosure - Leases - Summary of Maturity of Operating Lease Liabilities (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesSummaryofMaturityofOperatingLeaseLiabilitiesDetail_1" roleURI="http://www.smithmicro.com/role/LeasesSummaryofMaturityofOperatingLeaseLiabilitiesDetail_1">
        <link:definition>0000069 - Disclosure - Leases - Summary of Maturity of Operating Lease Liabilities (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SegmentConcentrationandGeographicalInformationAdditionalInformationDetail" roleURI="http://www.smithmicro.com/role/SegmentConcentrationandGeographicalInformationAdditionalInformationDetail">
        <link:definition>0000070 - Disclosure - Segment, Concentration and Geographical Information - Additional Information (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SegmentConcentrationandGeographicalInformationWirelessRevenuesbyProductLineDetail" roleURI="http://www.smithmicro.com/role/SegmentConcentrationandGeographicalInformationWirelessRevenuesbyProductLineDetail">
        <link:definition>0000071 - Disclosure - Segment, Concentration and Geographical Information - Wireless Revenues by Product Line (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SegmentConcentrationandGeographicalInformationCompanyRevenueinDifferentGeographicLocationsDetail" roleURI="http://www.smithmicro.com/role/SegmentConcentrationandGeographicalInformationCompanyRevenueinDifferentGeographicLocationsDetail">
        <link:definition>0000072 - Disclosure - Segment, Concentration and Geographical Information - Company Revenue in Different Geographic Locations (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SubsequentEventsDetails" roleURI="http://www.smithmicro.com/role/SubsequentEventsDetails">
        <link:definition>0000073 - Disclosure - Subsequent Events (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
    </xs:appinfo>
  </xs:annotation>
  <xs:element id="smsi_FamilySafetyMember" abstract="true" name="FamilySafetyMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_NumberOfGeographicLocation" abstract="false" name="NumberOfGeographicLocation" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="smsi_FamilySafetySolutionCustomerMember" abstract="true" name="FamilySafetySolutionCustomerMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_WirelessBusinessSegmentMember" abstract="true" name="WirelessBusinessSegmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_AccruedPayrollAndBenefitsCurrent" abstract="false" name="AccruedPayrollAndBenefitsCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_IncreaseDecreaseInReservesAgainstAccountsReceivable" abstract="false" name="IncreaseDecreaseInReservesAgainstAccountsReceivable" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_StockIssuedDuringPeriodSharesStockWarrantsExercised" abstract="false" name="StockIssuedDuringPeriodSharesStockWarrantsExercised" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="smsi_ServiceProviderOneMember" abstract="true" name="ServiceProviderOneMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_TwoCustomerMember" abstract="true" name="TwoCustomerMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_DebtInstrumentInterestRateDefaultPercentage" abstract="false" name="DebtInstrumentInterestRateDefaultPercentage" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="smsi_EffectiveIncomeTaxRateReconciliationsNOLCarryforwards" abstract="false" name="EffectiveIncomeTaxRateReconciliationsNOLCarryforwards" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="smsi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedExpenses" abstract="false" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedExpenses" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_OrganizationBasisOfPresentationAndSummaryOfSignificantAccountingPoliciesLineItems" abstract="true" name="OrganizationBasisOfPresentationAndSummaryOfSignificantAccountingPoliciesLineItems" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="smsi_IncomeTaxReconciliationTaxExpenseCreditsForeign" abstract="false" name="IncomeTaxReconciliationTaxExpenseCreditsForeign" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="smsi_CustomerFourMember" abstract="true" name="CustomerFourMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsFairValuePerShare" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsFairValuePerShare" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:perShareItemType"/>
  <xs:element id="smsi_TaxCutsAndJobsActOf2017IncomeRelatedToGlobalIntangibleLowTaxedIncome" abstract="false" name="TaxCutsAndJobsActOf2017IncomeRelatedToGlobalIntangibleLowTaxedIncome" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_FairValueAdjustmentOfWarrantsAndDerivativeLiabilites" abstract="false" name="FairValueAdjustmentOfWarrantsAndDerivativeLiabilites" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_PercentageOfEmployeeCompensationForEmployeePayrollDeduction" abstract="false" name="PercentageOfEmployeeCompensationForEmployeePayrollDeduction" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="smsi_AuditInformationAbstract" abstract="true" name="AuditInformationAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="smsi_ServiceProviderTwoMember" abstract="true" name="ServiceProviderTwoMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_NonCashLeaseExpense" abstract="false" name="NonCashLeaseExpense" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_EarningsPerShareBasicAndDilutedEPSAbstract" abstract="true" name="EarningsPerShareBasicAndDilutedEPSAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="smsi_MaximumSharesPurchasedByEmployees" abstract="false" name="MaximumSharesPurchasedByEmployees" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="smsi_CommSuiteMember" abstract="true" name="CommSuiteMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_AvastPLCFamilySafetyMobileSoftwareBusinessMember" abstract="true" name="AvastPLCFamilySafetyMobileSoftwareBusinessMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedPayrollAndBenefits" abstract="false" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedPayrollAndBenefits" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_FiniteLivedIntangibleAssetsRemainingAmortization" abstract="false" name="FiniteLivedIntangibleAssetsRemainingAmortization" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_PaymentsRelatedToContingentConsideration" abstract="false" name="PaymentsRelatedToContingentConsideration" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_ProceedsFromFinancingArrangements" abstract="false" name="ProceedsFromFinancingArrangements" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_EntityAndBusinessDescriptionPolicyTextBlock" abstract="false" name="EntityAndBusinessDescriptionPolicyTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="smsi_HostedEnvironmentUsageFeesMember" abstract="true" name="HostedEnvironmentUsageFeesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_TwoThousandAndFifteenStockOptionPlanMember" abstract="true" name="TwoThousandAndFifteenStockOptionPlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_IssuanceOfDerivativeAndWarrants" abstract="false" name="IssuanceOfDerivativeAndWarrants" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_EmployeeStockPurchasePlanMember" abstract="true" name="EmployeeStockPurchasePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_PrincipalAndAgentConsiderationsPolicyTextBlock" abstract="false" name="PrincipalAndAgentConsiderationsPolicyTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="smsi_AwardsSettledInSharesAdjustmentsAgainstShareReserve" abstract="false" name="AwardsSettledInSharesAdjustmentsAgainstShareReserve" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="smsi_OneCustomersMember" abstract="true" name="OneCustomersMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_PercentageOfFairMarketValueOfShare" abstract="false" name="PercentageOfFairMarketValueOfShare" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="smsi_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageForfeitureRate" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageForfeitureRate" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="smsi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIncludingDerivativeLiabilitiesAndContingentConsiderationSettlements" abstract="false" name="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIncludingDerivativeLiabilitiesAndContingentConsiderationSettlements" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_WellsFargoBankNationalAssociationMember" abstract="true" name="WellsFargoBankNationalAssociationMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_FullValueAwardsMember" abstract="true" name="FullValueAwardsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_FairValueGainLossInLiability" abstract="false" name="FairValueGainLossInLiability" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_AdditionalWarrantsMember" abstract="true" name="AdditionalWarrantsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_WarrantAndDerivativeLiabilitiesNoncurrent" abstract="false" name="WarrantAndDerivativeLiabilitiesNoncurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_DeferredTaxAsset163jLimitation" abstract="false" name="DeferredTaxAsset163jLimitation" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_CircleMediaLabsIncMember" abstract="true" name="CircleMediaLabsIncMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_DeferredTaxLiabilitiesUnrealizedCurrencyTransactionGainsLoss" abstract="false" name="DeferredTaxLiabilitiesUnrealizedCurrencyTransactionGainsLoss" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_BusinessCombinationContingentConsiderationRollForward" abstract="true" name="BusinessCombinationContingentConsiderationRollForward" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="smsi_FiniteLivedIntangibleAssetExpectedAmortizationYearFiveAndThereafter" abstract="false" name="FiniteLivedIntangibleAssetExpectedAmortizationYearFiveAndThereafter" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_ThreeCustomerMember" abstract="true" name="ThreeCustomerMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_PartialValueAwardsMember" abstract="true" name="PartialValueAwardsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_OtherProductMember" abstract="true" name="OtherProductMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_ConvertibleDebtGrossNoncurrent" abstract="false" name="ConvertibleDebtGrossNoncurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_ViewSpotMember" abstract="true" name="ViewSpotMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_ContractWithCustomerServiceTransitionPeriod" abstract="false" name="ContractWithCustomerServiceTransitionPeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="smsi_IssuanceOfCommonStockInConnectionWithAcquisition" abstract="false" name="IssuanceOfCommonStockInConnectionWithAcquisition" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_PurchasePriceAllocationMember" abstract="true" name="PurchasePriceAllocationMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_ConsultingServicesAndOtherMember" abstract="true" name="ConsultingServicesAndOtherMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_SeniorSecuredConvertibleNotesMember" abstract="true" name="SeniorSecuredConvertibleNotesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_NotesAndWarrantsOfferingMember" abstract="true" name="NotesAndWarrantsOfferingMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_TransactionCosts" abstract="false" name="TransactionCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_StockIssuedDuringPeriodValueStockWarrantsExercised" abstract="false" name="StockIssuedDuringPeriodValueStockWarrantsExercised" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIncludingDerivativeLiabilitiesAndContingentConsiderationGainLossIncludedInEarnings" abstract="false" name="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIncludingDerivativeLiabilitiesAndContingentConsiderationGainLossIncludedInEarnings" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_SalesAndMarketingMember" abstract="true" name="SalesAndMarketingMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeitedIntrinsicValue" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeitedIntrinsicValue" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_ConvertibleDebtGross" abstract="false" name="ConvertibleDebtGross" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_WarrantsFairValueDisclosure" abstract="false" name="WarrantsFairValueDisclosure" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_MaximumStockValueOfSharesPurchasedByEmployees" abstract="false" name="MaximumStockValueOfSharesPurchasedByEmployees" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_CreditFacilityMember" abstract="true" name="CreditFacilityMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_OrganizationBasisOfPresentationAndSummaryOfSignificantAccountingPoliciesTable" abstract="true" name="OrganizationBasisOfPresentationAndSummaryOfSignificantAccountingPoliciesTable" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType"/>
  <xs:element id="smsi_TwoThousandFifteenOmnibusEquityIncentivePlanMember" abstract="true" name="TwoThousandFifteenOmnibusEquityIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_SummaryOfOperatingLeaseAssetsAndLiabilitiesTableTextBlock" abstract="false" name="SummaryOfOperatingLeaseAssetsAndLiabilitiesTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="smsi_RepaymentsOfFinancingArrangements" abstract="false" name="RepaymentsOfFinancingArrangements" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_ConvertibleDebtGrossCurrent" abstract="false" name="ConvertibleDebtGrossCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisePeriodFollowingTermination" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisePeriodFollowingTermination" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="smsi_StockAndAdditionalWarrantsOfferingMember" abstract="true" name="StockAndAdditionalWarrantsOfferingMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_TwoThousandFiveStockOptionPlanMember" abstract="true" name="TwoThousandFiveStockOptionPlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIncludingDerivativeLiabilitiesAndContingentConsiderationPurchases" abstract="false" name="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIncludingDerivativeLiabilitiesAndContingentConsiderationPurchases" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityValueIncludingDerivativeLiabilitiesAndContingentConsideration" abstract="false" name="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityValueIncludingDerivativeLiabilitiesAndContingentConsideration" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="smsi_CloudBasedUsageFeesMember" abstract="true" name="CloudBasedUsageFeesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="smsi_CumulativeLossPeriod" abstract="false" name="CumulativeLossPeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="smsi_BusinessCombinationContingentConsiderationArrangementsAdditionsToAmountOfContingentConsiderationLiability" abstract="false" name="BusinessCombinationContingentConsiderationArrangementsAdditionsToAmountOfContingentConsiderationLiability" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
</xs:schema>
