We present an analytical framework to assess the link layer throughput of multichannel Opportunistic Spectrum Access (OSA) ad hoc networks. Specifically, we focus on analyzing various combinations of collaborative spectrum sensing and Medium Access Control (MAC) protocol abstractions. We decompose collaborative spectrum sensing into layers, parametrize each layer, classify existing solutions, and propose a new protocol called Truncated Time Division Multiple Access (TTDMA) that supports efficient distribution of sensing results in “K out of N” fusion rule. In case of multichannel MAC protocols, we evaluate two main approaches of control channel design with 1) dedicated and 2) hopping channel. We propose to augment these protocols with options of handling secondary user (SU) connections preempted by primary user (PU) by 1) connection buffering until PU departure and 2) connection switching to a vacant PU channel. By comparing and optimizing different design combinations, we show that 1) it is generally better to buffer preempted SU connections than to switch them to PU vacant channels and 2) TTDMA is a promising design option for collaborative spectrum sensing process when K does not change over time.
One of the first works that gained insight into the general performance of OSA networks, considering impact of PU activity on blocking and throughput of the SU network was @cite_29 , where the capacity of a multichannel OSA system was assessed by comparing centrally coordinated versus random SU channel assignment. A spectrum sensing process was not considered. A similar problem was investigated in @cite_11 where the spectrum sharing gains for PU and SU networks were obtained for a distributed and multichannel ad hoc OSA network. Unfortunately, a zero delay spectrum sensing process was assumed with genie-aided channel selection, i.e. in every time slot the receiver knew of the exact channel the transmitter will use to send data [Sec. III-C1] srinivasa_twc_2008 .
@cite_29 @cite_11
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Because of the asynchronization between primary and secondary wireless networks, the synchronization between primary users (PUs) and secondary users (SUs) can be hardly guaranteed in nontime-slotted cognitive radio networks (CRNs). In this paper, we propose a novel framework for multichannel nontime-slotted CRNs, where the PUs randomly access and leave the licensed channels. Since the PUs cannot distinguish between primary and secondary signals, the PUs may sense a busy channel when the PUs start to reactivate during the SUs' transmission, thus generating a collision or entering the backoff stage. To guarantee the high-throughput transmission of the PUs and increase the channel utilization of the SUs, in this paper, we propose the wireless full-duplex spectrum sensing (FD-SS) scheme for SUs in multichannel nontime-slotted CRNs. Using our developed FD-SS scheme, the SUs can timely sense the PUs' reactivation during the same time when the SUs are transmitting their signals. Then, based on our proposed wireless FD-SS scheme, we further develop and analyze the wireless full-duplex cognitive medium access control (FDC-MAC) protocol for multichannel nontime-slotted CRNs. We conduct extensive numerical analyses, showing that our developed FD-SS scheme and FDC-MAC protocol can efficiently guarantee the high-throughput transmission of the PUs and increase the channel utilization of the SUs without requiring the synchronization between the PUs and the SUs over the multichannel nontime-slotted CRNs. In this paper, different control channel (CC) implementations for multichannel medium access control (MAC) algorithms are compared and analyzed in the context of opportunistic spectrum access (OSA) as a function of spectrum-sensing performance and licensed user activity. The analysis is based on a discrete Markov chain model of a subset of representative multichannel OSA MAC classes that incorporates physical layer effects, such as spectrum sensing and fading. The analysis is complemented with extensive simulations. The major observations are given as follows: 1) When the CC is implemented through a dedicated channel, sharing such dedicated channel with the licensed user does not significantly decrease the throughput achieved by the OSA network when the data packet sizes are sufficiently large or the number of considered data channels is small. 2) Hopping OSA MACs, where the CC is spread over all channels, are less susceptible to licensed user activity than those with a dedicated CC (in terms of both average utilization and on off times). 3) Scanning efficiency has a large impact on the achievable performance of licensed and OSA users for all analyzed protocols. 4) The multiple rendezvous MAC class, which has yet to be proposed in OSA literature, outperforms all the multichannel MAC designs analyzed in this paper.