Spectrum Sharing MAC-layer Protocols：MAC层协议的频谱共享.pptVIP

Spectrum Sharing MAC-layer ProtocolsSang-Yoon ChangECE 439 Spring 2021 MotivationBandwidth becoming scarcer and more valuableIncreased demands on wireless applicationsUsers demand higher performanceDynamically accessing multiple channels can increase spectrum efficiencyOur goal is to support multiple transmissions and increase performance by mitigating interference FCC Spectrum Allocation Chart Spectrum UtilizationA snapshot of spectrum utilization up to 6 GHz in an urban area at mid-day [1] BackgroundCognitive radioSecondary users operating on licensed BandRequired to detect primary users’ signals (physical-layer)Avoid and yield the channel use to primary users (MAC-layer)In addition, coordination with other secondary usersOther Spectrum Sharing Techniques Ultra WideBand (UWB) CommunicationUnlicensed Band, e.g., ISM band Project OverviewRandom access protocol without coordination [2]Centralized channel allocation algorithm [3]Distributed channel allocation algorithm [4],[5]Single radio per user [6],[7]Sensing overhead / limitations [7],[8]Diverging from traditional slotted channelization [7],[10],[11],[12]Selfish users [14]MMAC [6], HMAC [7] SWIFT [10] Hidden-Terminal ProblemIn single-channel environment, IEEE 802.11 DCF, busy-toneAssumed single radio per userIEEE 802.11 DCF in multi-channel environmentC does not hear the CTS(2) from B, and thus collisionIf multiple radios per user, Dynamic Channel Assignment (DCA) by Wu [9]Needs complex hardware MMAC ProtocolMulti-Channel MAC (MMAC) by So and Vaidya [6]Single radio per userBuild on IEEE 802.11 PSM protocol (beacon interval, ATIM)Requires global synchronizationIn ATIM window, Agree on a channel according to Preferable Channel List (High, Medium, Low)ATIM-RES to notify the channel reservation Beacon Interval MMAC PerformanceCompared to DCA [9] and IEEE 802.11WLAN (above) and multi-hop (below) environmentAlso observed packet delayCBR trafficPacket size = 512 BytesBeacon interval = 100 msATIM window size = 20 ms3