Abstract-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.

Abstract-This paper compares, through analysis and simulation, a number of multichannel MAC protocols. We first classify these protocols into four categories based on their principles of operation: Dedicated Control Channel, Common Hopping, Split Phase, and Parallel Rendezvous protocols. We then examine the effects of the number of channels and devices, channel switching times, and traffic patterns on the throughput and delay of the protocols. Here are some of the conclusions of our study: 1) Parallel Rendezvous protocols generally perform better than Single Rendezvous protocols, 2) the Dedicated Control Channel protocol can be a good approach with its simplicity when the number of channels is high and the packets are long, and 3) the Split Phase protocol is very sensitive to the durations of the control and data phases. Our study focuses on a single collision domain.

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Abstract-1 In ISM bands, many wireless protocols proliferate such as 802.11, Bluetooth, and ZigBee. However, these incompatible protocols create complex coexistence and connectivity problems. If the same trend continues, similar interference and performance problems will continue to exist in future unlicensed bands. As new unlicensed bands open up, one can take a different approach to spectrum sharing. Instead of proposing a new MAC protocol for each type of application, we propose a family of parameterized MAC protocols called WiFlex that can tailor to different application needs ranging from wireless sensors to media center. Yet, these protocols within this family are compatible with each other to allow communication and spectrum-sharing coordination among different types of devices. We envision this family to be based on an OFDM-like multichannel physical layer.The contribution of this paper includes the discovery of an asynchronous split phase (ASP) protocol with dynamic priority support. This protocol enables powerful devices to achieve a high throughput and protects low power devices with urgent but only occasional transmissions. It is distributed and data collision-free. Moreover, it can support low delays for real time applications.The performance of the protocols are evaluated using an extension of NS-2. The results demonstrate the coexistence of devices with disparate radio characteristics and the support of applications with different requirements with good performance.