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We are motivated to exploit the broadcast nature of a radio medium in combating its unreliable and time-varying characteristics. This leads to cooperative transmission where a neighbor node keeps a copy of an overheard packet and helps in retransmitting the overheard packet to its intended destination when the original transmission fails. Cooperative transmission improve wireless network performance...
Exact average capacity results for L-branch coherent equal-gain combining (EGC) in correlated and uncorrelated fading channels are not known. This paper develops a novel framework (approach) for capacity analysis of L-branch EGC in generalized fading channels. In addition, Gamma shadowed generalized Nakagami-m fading model is proposed in order to statistically model the fading environments in high...
The throughput of conventional wireless multicast systems is limited by the multicast user with the lowest channel quality, which leads to a very low throughput especially if the number of users is large. In this paper, we show that hybrid-automatic repeat request with Chase combining (HARQ-CC) is a promising technique to overcome this problem and optimize the transmission rate of wireless multicast...
In this paper, we propose an antenna selection algorithm for down link MIMO SDMA OFDM system. For each user, the data rate corresponding to each transmit antenna is maximized using the optimal bit loading algorithm. A data rate matrix is constructed and used for the antenna selection algorithm assuming the base station (BS) knows the signal-to-noise ratio on all antenna-user pairs of all sub-carriers...
The performance of dual-hop Decode-and-Forward relaying with relay selection (RS) and repetitive transmission is studied over Nakagami-m fading channels. Closed-form expressions for the moment generating function of RS-based transmission with maximal-ratio diversity at the destination and repetitive transmission with selection diversity (SD) are derived. We obtain the outage probability (OP) and the...
This paper proposes a new combinational technology which is feasible to apply physical-layer network coding (PNC) to wireless fading channel. The key step of PNC is that sources broadcast signals simultaneously without orthogonal scheduling. Naturally, the signals overlap in the free space at the receivers. Since the signals from different sources are mutual independent, rooted on this rational assumption,...
In this paper, three cooperative relaying schemes are proposed for relay networks comprised of two source terminals and multiple relays, each with single antenna. The new relaying schemes, corresponding to the maximum ratio combining of the downlink and uplink channels, phase rotation of the received signals at relays, and the channel gain equalization, are designed based on the maximization of the...
This paper introduces a wireless access system for the wide area ubiquitous network (WAUN), which is a large cell-based public sensor network, and provides feasibility study results gained through field tests. The wireless access system uses several key technologies to accommodate widely dispersed small simple terminals. First, to realize the large cell radius of several kilometers, space and site...
This paper considers the problem of routing packets across a multi-hop wireless network while ensuring throughput optimality. One of the main challenges in the design of throughput optimal routing policies is identifying appropriate and universal Lyapunov functions with negative expected drift. The few well-known throughput optimal routing policies in the literature are constructed using simple quadratic...
WiMax is one of the most important technologies for providing a broadband wireless access (BWA) in a metropolitan area. The use of OFDM transmissions has been proposed to reduce the effect of multipath fading in wireless communications. Moreover, multiple access is achieved by resorting to the OFDMA scheme. Adaptive subcarrier allocation techniques have been selected to exploit the multiuser diversity,...
In this paper, a pattern diversity antenna with switched parasitic elements is presented for wireless LAN application. A wire meander-line antenna on top of a circular metallic ground plane is designed and used as the main radiator. Some conductive rods are installed on the ground plane, around the antenna. Connecting and disconnecting of the rods to the ground plane stirrers the antenna farfield...
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