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...o , we get (78) Since is nonnegative, the second derivative is negative, hence, the cost function in (77) is concave in and the necessary conditions (the Karush–Kuhn–Tucker conditions) for optimality =-=[32]-=- are also sufficient. Equating the first derivative in (78) to zero, the solution is given by (79) From the first constraint in (74), the minimum value for that guarantees the stability of queue 1 in ...

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... queueing theory, relay channel, stability analysis, stability region. I. INTRODUCTION COOPERATIVE diversity is a recently emerged technique for wireless communications that has gained wide attention =-=[1]-=-. As a new communication paradigm for wireless networks, the impact of cooperation at different network layers needs to be studied and understood. Most of the work on cooperative communications has fo...

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...of cooperative diversity has been also explored in [5] using an information-theoretic framework. Achievable capacity and coding strategies for wireless relay channels have been considered recently in =-=[3]-=-. Beside characterizing cooperation gains based upon an information-theoretic framework, as in the previously cited works, the symbol-error-rate performance for cooperative communications was analyzed...

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...and thus we render to a special case to capture the insights of this scenario. Let the outage be defined as the event that the mutual information between two terminals is less than some specific rate =-=[29]-=-. If the transmitted signals are Gaussian, then according to our channel model, the mutual information between terminal and terminal is given by SNR . The outage event for this case is defined as (50)...

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...ration. Digital Object Identifier 10.1109/TIT.2007.904784 virtual multiple-input multiple-output (MIMO) systems. The diversity–multiplexing tradeoff of cooperative diversity has been also explored in =-=[5]-=- using an information-theoretic framework. Achievable capacity and coding strategies for wireless relay channels have been considered recently in [3]. Beside characterizing cooperation gains based upo...

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...f (1) and (2) , the queue is called substable. If the arrival and service processes of a queueing system are strictly stationary, then one can apply Loynes’s theorem to check for stability conditions =-=[16]-=-. This theorem states that if the arrival process and the service process of a queueing system are strictly stationary, and the average arrival rate is less than the average service rate, then the que...

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...side characterizing cooperation gains based upon an information-theoretic framework, as in the previously cited works, the symbol-error-rate performance for cooperative communications was analyzed in =-=[6]-=-, [7], for a single-relay scenario, and later in [9] for the multiple-relay scenario. The impact of cooperation on extending coverage area in wireless networks has been investigated in [10] and [11] i...

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... function of the fading realization is given by SNR , then the outage event is the event that SNR , and SNR denotes the outage probability. This definition is equivalent to the capture model in [19], =-=[18]-=-. The SNR threshold is a function of different parameters in the communication system; it is a function of the application, the data rate, the signal processing applied at encoder/decoder sides, error...

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... proof of the lemma. 2) The Symmetric -Terminals Case: Stability analysis for the general -terminal case is very complicated. For the ALOHA case, only bounds on the stability region have been derived =-=[22]-=-, [27]. In this paper, we only focus on the symmetric scenario. We define the dominant system for -terminal CCMA-S, , as follows. and the original system are identical, except that, the relay does not...

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...ntly, the concept of cognitive radio has been introduced to allow the utilization of unused channel resources by enabling the operation of a secondary system overlapping with the original system (see =-=[33]-=- and references therein). In our work, we propose a novel cognitive multiple-access strategy with the concept of cooperation. In the proposed protocol, the cognitive relay tries to “smartly” utilize t...

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...ation at higher network layers. Cooperation in random-access networks has been considered in [12]–[14]. In [12], the authors proposed a distributed version of network diversity multiple-access (NDMA) =-=[31]-=- protocol and they provided pairwise error probability analysis to demonstrate the diversity gain. In [13] and [14], the authors presented the notion of utilizing the spatial separation between users ...

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...information-theoretic framework, as in the previously cited works, the symbol-error-rate performance for cooperative communications was analyzed in [6], [7], for a single-relay scenario, and later in =-=[9]-=- for the multiple-relay scenario. The impact of cooperation on extending coverage area in wireless networks has been investigated in [10] and [11] in which distributed and centralized relay assignment...

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...R as a function of the fading realization is given by SNR , then the outage event is the event that SNR , and SNR denotes the outage probability. This definition is equivalent to the capture model in =-=[19]-=-, [18]. The SNR threshold is a function of different parameters in the communication system; it is a function of the application, the data rate, the signal processing applied at encoder/decoder sides,...

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...ressed for ALOHA systems initially in [20], and later in [21], where the dominant system approach was explicitly introduced. Many other works followed that to study the stability of ALOHA [15], [22], =-=[27]-=-, and [28]. Characterizing the stable throughput region for interacting queues with terminals is still an open problem. In CCMA-S, the interaction among the queues arises due to the role of the relay ...

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...m’s queues we resort to a stochastic dominance approach. Analyzing the stability of interacting queues is a difficult problem that has been addressed for ALOHA systems initially in [20], and later in =-=[21]-=-, where the dominant system approach was explicitly introduced. Many other works followed that to study the stability of ALOHA [15], [22], [27], and [28]. Characterizing the stable throughput region f...

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...has been addressed for ALOHA systems initially in [20], and later in [21], where the dominant system approach was explicitly introduced. Many other works followed that to study the stability of ALOHA =-=[15]-=-, [22], [27], and [28]. Characterizing the stable throughput region for interacting queues with terminals is still an open problem. In CCMA-S, the interaction among the queues arises due to the role o...

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...e work on cooperative communications has focused on the physical layer aspects of the problem. Cooperation protocols for the single-relay case were developed and analyzed in [1], and later in [2] and =-=[4]-=- distributed space–time codes were developed and analyzed for multiple-relay scenarios. In the previous works it was demonstrated that full diversity gain can be achieved by forming such Manuscript re...

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...bility of the system’s queues we resort to a stochastic dominance approach. Analyzing the stability of interacting queues is a difficult problem that has been addressed for ALOHA systems initially in =-=[20]-=-, and later in [21], where the dominant system approach was explicitly introduced. Many other works followed that to study the stability of ALOHA [15], [22], [27], and [28]. Characterizing the stable ...

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...characterizing cooperation gains based upon an information-theoretic framework, as in the previously cited works, the symbol-error-rate performance for cooperative communications was analyzed in [6], =-=[7]-=-, for a single-relay scenario, and later in [9] for the multiple-relay scenario. The impact of cooperation on extending coverage area in wireless networks has been investigated in [10] and [11] in whi...

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...analyzed in [6], [7], for a single-relay scenario, and later in [9] for the multiple-relay scenario. The impact of cooperation on extending coverage area in wireless networks has been investigated in =-=[10]-=- and [11] in which distributed and centralized relay assignment protocols have been developed, respectively. Few works started to study the impact of cooperation at higher network layers. Cooperation ...

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... [12], the authors proposed a distributed version of network diversity multiple-access (NDMA) [31] protocol and they provided pairwise error probability analysis to demonstrate the diversity gain. In =-=[13]-=- and [14], the authors presented the notion of utilizing the spatial separation between users in the network to assign cooperating pairs (also groups) to each other. In [14], spread-spectrum random-ac...

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...etwork parameter that may affect the tradeoff between rate and reliability of communication. Delay analysis for interacting queues is a notoriously hard problem that has been investigated in [25] and =-=[26]-=- for ALOHA. We consider a symmetric two-user scenario when analyzing the delay performance of the proposed protocols. Our theoretical results demonstrate significant performance gains of the proposed ...

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...lay assignment protocols have been developed, respectively. Few works started to study the impact of cooperation at higher network layers. Cooperation in random-access networks has been considered in =-=[12]-=-–[14]. In [12], the authors proposed a distributed version of network diversity multiple-access (NDMA) [31] protocol and they provided pairwise error probability analysis to demonstrate the diversity ...

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...in [6], [7], for a single-relay scenario, and later in [9] for the multiple-relay scenario. The impact of cooperation on extending coverage area in wireless networks has been investigated in [10] and =-=[11]-=- in which distributed and centralized relay assignment protocols have been developed, respectively. Few works started to study the impact of cooperation at higher network layers. Cooperation in random...

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...raction of the time. Let denote a resource-sharing vector, where is the fraction of the time allocated to terminal , or it can represent the probability that terminal is allocated the whole time slot =-=[30]-=-. In this work, we use the later notation that allows us to consider fixed duration time slots with continuous values of the resource-sharing vector. A time frame is defined as consecutive time slots....

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...ssignment protocols have been developed, respectively. Few works started to study the impact of cooperation at higher network layers. Cooperation in random-access networks has been considered in [12]–=-=[14]-=-. In [12], the authors proposed a distributed version of network diversity multiple-access (NDMA) [31] protocol and they provided pairwise error probability analysis to demonstrate the diversity gain....

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...ure and network parameter that may affect the tradeoff between rate and reliability of communication. Delay analysis for interacting queues is a notoriously hard problem that has been investigated in =-=[25]-=- and [26] for ALOHA. We consider a symmetric two-user scenario when analyzing the delay performance of the proposed protocols. Our theoretical results demonstrate significant performance gains of the ...