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In this paper, we investigate the average symbol error probability (SEP) of fixed decode-and-forward relay networks over independent but not identically distributed Nakagami-m fading channels. We have derived closed form expression of SEP for general rectangular quadrature amplitude modulation (QAM) under relay selection scheme where only the best relay forwards message from the source to the destination...
The conventional cooperative protocols have to face some problems in practical broadcast and multicast systems because feedback channel is unavailable. An adaptive cooperative relay protocol, which can be adopted in future broadcast systems, is proposed in this paper. The outage probability performance of this protocol is analyzed over Nakagami-m fading channel, and the asymptotic expression of outage...
Many previous studies have shown that traditional TCP slow-start algorithm suffers performance degradation in high-speed and long-delay networks. This paper presents a sender-side enhancement, which makes use of TCP Vegas congestion-detecting scheme to monitor the router queue, and accordingly refines slow-start window evolution by introducing a two-phase approach to probe bandwidth more efficiently...
This paper presents a performance comparison between a circuit-based CDMA2000 1x voice system and LTE VoIP system, in terms of capacity, air link latency and link budget. The performance comparison is based on link and network level simulations using a common evaluation methodology. The voice capacity of existing CDMA2000 1x is about 14% better than that of VoIP over LTE (based on 3GPP-Release 8)...
We deal with positioning of node in wireless sensor network (WSN) using received signal strength (RSS) when there is no priori knowledge about path-loss exponent and transmission power. Since the RSS decreases on the average with distance, it carries some information about the distance to an unknown node. By ordering the RSS's, we conclude that there are some convex sets where the position of the...
In this paper, for the first time, an Ant Colony Optimization (ACO) based algorithm is used to solve the bit and subcarrier resource allocation problem of single-cell OFDMA systems. It results in a directed multigraph if the vertexes are used to represent the subcarrier and each path corresponds to a possible chosen modulation index of a specific user. Earlier studies which applied evolutionary algorithms...
In this paper we study the problem of energy efficient packet scheduling in wireless fading channels with hard delay constraints. Each packet has a strict delay constraint of D time slots and it has to be delivered before its delay deadline. Optimal scheduling of each packet now depends on future Channel State Information (CSI) which is not available. We develop the upper and lower bounds on the optimal...
Femtocell is attracting an increasing interest in the telecommunication sectors. In this paper, we study the efficient resource allocation in femtocell networks with completed closed access method. The interaction between a macrocell and its underlying femtocells is identified, characterized, and qualified. The study answers the fundamental question in the femtocell networks: how to allocate spectrum...
In this paper, we study the relay assignment problem in cooperative wireless networks with self-interested nodes. Such systems should be organized from the point of view of efficiency, stable and providing consistent incentives to all nodes. We propose a cooperation mechanism which includes the cooperative relationship formation stage and cooperation maintenance stage. The cooperative relationship...
Statistical models for handover scenarios are necessary in order to identify key parameters and to allow proper benchmarking for handover techniques. This is quite a difficult task, since many assumptions have to be made, resulting in a loss of generality. Efforts towards the generation of such models were already made. Although these models show insights into trade offs, they leave some open questions...
In this paper, we consider a half-duplex Gaussian relay channel where the noises at the relay and destination are arbitrarily correlated. For this generalized relay channel, we first evaluate the cut-set bound as well as the achievable rates with three existing relay schemes: Decode-and-Forward (DF), Compress-and-Forward (CF), and Amplify-and-Forward (AF), with performance comparison under various...
Key distribution plays an important role in wireless sensor networks (WSNs), for information must be kept secure, even in an environment with limited storage ability and low data processing speed. However, it is a challenge to work in such a harsh requirement environment, the traditional key management scheme such as key distribution center (KDC) and public key cannot be used. Key pre-distribution...
With its new features such as multi-homing and multi-streaming the Stream Control Transmission Protocol (SCTP) has become a promising candidate as a general-purpose transport layer protocol. Multi-homing in an SCTP association can make concurrent multi-path transfer an appealing candidate to satisfy the ever increasing user demands for bandwidth. Multiple streams provide an aggregation mechanism to...
In this paper an improved iterative algorithm is proposed for distributed transmit beamforming to achieve carrier phase alignment at the receiver. The transmitters adjust their phase offsets based on one-bit feedback from the receiver in each time slot. The proposed algorithm has an improvement in the convergence speed of phase alignment compared to a previously proposed algorithm in the literature...
Release-8 (Rel-8) EPS (Evolved Packet System) introduced a multi access 3GPP system where different heterogeneous access systems are connected to a common core network. However, in the system, the subscriber cannot communicate using multiple accesses simultaneously. Mobile devices with multiple interfaces are becoming commonly available and the set of applications running on the devices is diversifying...
The Mojette transform and the finite Radon transform (FRT) are discrete data projection methods that are exactly invertible and are computed using simple addition operations. Incorporation of a known level of redundancy into data and projection spaces enables the use of the FRT to recover the exact, original data when network packets are lost during data transmission. The FRT can also be shown to...
In this paper, an efficient implementation of the interior point algorithm recently proposed by Wadayama [5] for linear programming (LP) decoding of low-density parity-check (LDPC) codes is presented. The main idea behind the modification is to approximate the barrier function for the fundamental polytope defining the code so that it contains only one linear constraint for each of the parity-check...
Rings overlay is a class of multi-path routing structure for wireless sensor networks that exploits the broadcast nature of wireless communication to cope with communication failures. While the rings overlay aims to create multiple propagation paths for sensor nodes to transport data, the sensor nodes in the ring next to the base station inherently have only a single propagation path to the base station...
We derive both the optimal and the game-theoretic (cheat-proof) solutions in closed form, to a problem of distributed access with power control in a pairwise interaction network. In this network, each node has an energy constraint in a fixed time unit for using different power levels in each access attempt competing with a randomly selected node. The one with larger power level wins the access. The...
In this paper, we consider optimal power allocation (OPA) for distributed space-time coded two-way relay networks. Each relay transmits a scaled version of the linear combinations of the received symbols and their conjugates, and the scaling factor is based on automatic gain control (AGC) at the relays. We show that solving the OPA across relays to minimize the average conditional PEP of the destination...
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