This paper is about the optimization of beamforming weights in the nonlinear array antenna system. We consider the multi-objective optimization using the evolutionary algorithm. First, we constrain two variables - the...
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ISBN:
(纸本)0780385217
This paper is about the optimization of beamforming weights in the nonlinear array antenna system. We consider the multi-objective optimization using the evolutionary algorithm. First, we constrain two variables - the width of the main-lobe, the level of the side-lobe. Second, we constrain an additional variable, the energy of beamforming weights, on the former system. In each case, we compute the costs of beamforming weights in each generation. At the end of generations, we can get the Pareto frontier which means the optimal solution set. To demonstrate the performance of the proposed optimization, we compare the results between the proposed algorithm and the conventional window method.
A noncoherent reduced state differential sequence detection (RSDSD) for continuous phase modulation (CPM) is proposed in this paper. This method makes use of the reduced state trellis based on reduced state sequence d...
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ISBN:
(纸本)0780385233
A noncoherent reduced state differential sequence detection (RSDSD) for continuous phase modulation (CPM) is proposed in this paper. This method makes use of the reduced state trellis based on reduced state sequence detection (RSSD) and performs one-symbol differential Viterbi detection. The minimum Euclidean distance of the reduced state trellis is analyzed for full response CPM and partial response CPM. Bit error rates of RSSD and RSDSD are simulated for octal 2RC signal with h=1/8 in the AWGN channel and comparisons are made between the different RSSD schemes and between coherent RSSD and noncoherent RSDSD with Doppler frequency shifts. Although our proposed scheme is degraded by 2 dB at 10/sup -3/ bit error rate as compared with coherent detection, it is more appropriate and robust when the carrier recovery is difficult.
A vast majority of communications in a network occurs between pairs of nodes, each such interaction is termed a call. The job of a call control algorithm is to decide which of a set of calls to accept in the network s...
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This work describes the design and implementation of an 8-bit fixed point digital signal processor core in Verilog HDL. The architecture exploits the principles of pipelining and parallelism in order to obtain high sp...
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A quadrature rule for the finite Hilbert Transform via trapezoid type inequalities is obtained. Some numerical experiments for different divisions of the interval [a, b] are also presented.
A quadrature rule for the finite Hilbert Transform via trapezoid type inequalities is obtained. Some numerical experiments for different divisions of the interval [a, b] are also presented.
With increasing demand for multimedia and real-time applications, local area network (LAN) technologies are rapidly being upgraded to support Quality-of-Service (QoS). Many QoS-enabled LANs are making use of resource ...
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With increasing demand for multimedia and real-time applications, local area network (LAN) technologies are rapidly being upgraded to support Quality-of-Service (QoS). Many QoS-enabled LANs are making use of resource allocation mechanisms that can discriminate among traffic classes of different priorities. When such LANs are interconnected by bridges to form an extended LAN, it is necessary to upgrade the bridges so that they are QoS-enabled as well. For example, the IEEE 802.1p standard defines a framework for priority queuing in bridges. Alternatively, frame forwarding decisions at the link layer may be modified to recognize frame priorities and alternate paths may be used for differentiating QoS. In this paper, we describe a novel bridge protocol that can forward frames of different priorities using different paths. Our protocol ensures that the forwarding path of a higher priority frame is never longer than the forwarding path of a lower priority frame.
Poor bandwidth utilization of multihop ad hoc networks is a critical bottleneck that needs to be overcome before many interesting applications can be launched. In this paper we first propose a unified differentiation ...
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Poor bandwidth utilization of multihop ad hoc networks is a critical bottleneck that needs to be overcome before many interesting applications can be launched. In this paper we first propose a unified differentiation MAC architecture to support prioritized service. Based on the architecture we further propose a performance enhancement scheme for multihop wireless ad hoc networks. Unlike other schemes that may introduce extra overhead or may be incompatible with IEEE 802.11, our enhancement modifies the original IEEE 802.11 MAC and maintains the compatibility. By defining the interframe space and the contention window size as functions of the number of retransmissions, our enhanced scheme is able to give high priority to nodes which have retried many times to access the medium. As a result, it improves the overall performance in terms of end-to-end delay, packet deliver ratio, decreases the packet-dropping rate, and reduces the unnecessary routing discovery and update.
In this paper, the IEEE 802.11 multiple access control (MAC) protocol was modified for use in multi-channel, multi-hop ad hoc networks through the use of a new channel-status indicator. In particular, in the modified ...
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In this paper, the IEEE 802.11 multiple access control (MAC) protocol was modified for use in multi-channel, multi-hop ad hoc networks through the use of a new channel-status indicator. In particular, in the modified protocol, the RTS/CTS dialogue is exchanged on the common access control channel and data packets are transmitted on a selected traffic channel. We have evaluated the improvement due to the multi-channel use and we report in this paper on the results of the per-node throughput and the end-to-end delay for different network sizes. Using these results, we were able to propose a number of per-node throughput scaling laws. Our simulation results show that the per-node throughput with multiple channels for the fully connected, the line, and the grid ad hoc network topologies increases by 90% to 253%, by 47%, and by 139% to 163%, respectively, for networks with 16 to 64 nodes, as compared with that of a single channel.
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