David Brady James C Preisig
Much of the development of the preceding chapters is applicable to a broad range of wireless networks, although there is a strong emphasis on radio-frequency RF systems and their applications. And while underwater acoustic channels and systems share many features with their RF counterparts, there are also important differences. In this chapter, we describe the special characteristics of underwater acoustic channels and show how they impact system design. The underwater acoustic channel UAC is...
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Figure 6.6 Abstracted view of the service from the perspective of the bitway. shown in Figure 6.6. The stream of packets is logically divided into substreams, which are visible to the bitway. The integrity of substreams is maintained across multiple links see Section 6.3 . Each substream is associated with distinct QoS and rate attributes established by negotiation with the application. The QoS attributes are aggregated values from the individual links, so that each substream on each link has a...
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Figure 2.2 Multi-input multi-output MIMO channel and receiver model. Figure 2.2 Multi-input multi-output MIMO channel and receiver model. where b- is the K-vector of transmitted symbols at time i that is, b- is the zth column of the matrix b introduced in Section 2.1 and l T is the symbol rate, assumed to be the same for all users. The fcth component of bif denoted as bt k, is the zth transmitted symbol from user k. We assume that the signaling waveforms corresponding to each user, as well as...
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s n arg max 11 s n n N s n , which decouples to P separate optimizations s n argmax sl n n N - st n 2 i 1, 2, P. 3.43 The linear ZF equalizer can be obtained by letting Af 0 0 in 3.41b , i.e., it is given by 3.41 - 3.43 where 3.41b is replaced by i n A n n- l l n H n A n n - lJH n 1. 3.2.5.1 Linear Equalization for LTI Channels In this section, we examine linear equalization schemes for multiuser LTI channels that can be used to combat the three effects of noise, ISI, and MAI. These equalizers...
Architectural Principles for Multimedia Networks
Paul Haskell David G. Messerschmitt Louis Yun Many treatments of wireless communications focus on a wireless link as an isolated entity Our concern here is with networks that support all multimedia services including data, graphics, audio, images, and video for tetherless not physically wired to the network , nomadic able to access the network from many locations , and mobile accessing the network while moving users. Such a network is termed an integrated-services multimedia network with...
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offering an attractive arena for the fusion of sound theory with important applications and promises to be a research area with high impact. 1 S. Lin and D. J. Costello, An Introduction to Error-Correcting Codes. Englewood Cliffs, NJ Prentice-Hall, 1984. 2 C. E. Shannon, A mathematical theory of communication ' Bell Syst. Tech. Journal, vol. 27, pp. 379-423,1948. 3 T. Berger, Rate Distortion Theory. Englewood Cliffs, NJ Prentice Hall, 1971. 4 T. M. Cover and J. A. Thomas, Elements of...
Edge vs Link Architecture for Service Layer
In Section 6.2, we addressed the problem of separating the designs of the service from the bitway while leaving open most possibilities for JSCC. Our motivation was to allow the flexibility to substitute freely the service or bitway realizations. In this section, we consider a related set of issues in the provision of CM services through two or more heterogeneous subnets. Many of the issues addressed in Section 6.2 become more important. Consider two basic architectures, illustrated in Figure...
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31 A. J. van der Veen, S. Talwar, and A. Paulraj. Blind identification of FIR channels carrying multiple finite alphabet signals. Proc. Int. Conf Acoust., Speech, Signal Processing, 2 1213-1216, Detroit, 1995. 32 M. C. Vanderveen, C. Papadias, and A. Paulraj. Joint angle and delay estimation JADE for multipath signals arriving at an antenna array IEEE Commun. Tetters, 1 1 12-14, January 1997. 33 M. D. Yacoub. Foundations of Mobile Radio Engineering. CRC Press, Boca Raton, Florida, 1993. 34 E....
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Thus, the bit-error rate achieved depends strongly on the channel gain a. If the fading is sufficiently severe that a drops below some minimum SNR level necessary for adequate performance, then the system is said to experience an outage '8 Since with a complex-valued Gaussian amplitude the SNR 1.8 is an exponentially distributed random variable with mean then for a given threshold the outage probability can be readily calculated as the integral under the tail of the exponential density. This...
Concluding Remarks 1
The most important point of this chapter is that in an integrated-services multimedia network, it is advantageous to take an overall systems perspective, rather than designing wireless access networks in isolation. We have seen how, by coordinating the design of the backbone network, terminals, and servers with the wireless access network, greater traffic capacity can be achieved subject to subjective quality objectives. At the same time, it is important to adhere to good principles of...
and Effective Bandwidth
As the preceding chapters have emphasized, the mobile wireless environment provides several unique challenges to reliable communication not commonly found in wireline networks. These include scarce bandwidth, limited transmit power, interference between users, and time-varying channel conditions. A central problem in the design of wireless networks is how to use the limited resources most efficiently in such adverse environments, in order to meet the quality-of-service QoS requirements of...
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The z, s th integral in 7.1 is equal to the individual expected distortion if index i is sent i.e., given that x E y . These individual contributions are summed among all source symbols and averaged over two possible channel states, yielding the total expected distortion. To solve the constrained problem of 7.1, 7.2 we introduce a Lagrange multiplier X 75 and solve the unconstrained problem of the form min J M, r, rs, C E D X, X a J, 7.4 where X gt 0 is chosen to satisfy the energy constraint...
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Figure 6.5 Abstracted model of the bitway from the perspecti ve of the service, for a single substream. Since the bitway core function is to transport packets, the abstract view should focus on the fundamental packet transport impairments of corruption, loss, and delay. A basic model incorporating these three elements is shown schematically in Figure 6.5. Often, the service will be interested in the temporal properties of these impairments that is, a characterization of whether impairments like...