Introduction to Wireless Local Loop: Broadband and Narrowband Systems (2nd Edition)
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Featuring developing technologies, updated market forecasts, and current regulatory initiatives, this text aims to keep the reader at the forefront of emerging products, services and issues affecting the field of wireless local loop (WLL) technology. The second edition includes new chapters on WLL deployment, the WLL market, and a substantial review of broadband technologies, as well as new sections on prediction of user requirements and the emerging UMTS standard.
corrects one error in every three bits but triples the bandwidth required. Considerably more efficient schemes are available. There are schemes that detect errors but do not correct them. In the simple example in the preceding paragraph, if the message is repeated only twice and the repetition of a given bit is not the same as the original transmission, it is clear that an error has occurred, but it is not possible to say which transmission is in error. In an error-detection scheme, the receiver
Multiplication− −0 −2 −2 −0 −0 −2 −2 −0 =8 Transmit (data = 0) −1 −1 −1 −1 −1 −1 −1 −1 − Interferer (data = 0) −1 −1 −1 −1 −1 −1 −1 −1 − Received signal− −2 −0 −0 −2 −2 −0 −0 −2 − Receiver codeword− −1 −1 −1 −1 −1 −1 −1 −1 − Multiplication− −2 −0 −0 −2 −2 −0 −0 −2 = −8 So whatever is transmitted by the interferer and by the wanted user, the correlator produces the same result as if there were no interferer. Clearly the signals are
costs and the extent to which the network is capacity limited. Certainly, in a highly capacity-limited situation, CDMA systems should prove less expensive. Other situations are less clear. Part IV looks at the relative system costs when different systems are compared; Part V compares costs in the examination of business cases. 9.3.7 Bandwidth flexibility CDMA systems can increase user bandwidth simply by reducing G. TDMA systems also can be bandwidth flexible by assigning more than one TDMA
increased, just the spectrum required. The FH is defined as fast when the jumps occur more than once in a bit period and slow otherwise. At the moment, fast FH is restricted to military applications and is not considered further here. FH has been introduced in the context of TDMA systems that move from channel to channel to avoid interference. By some quirk of history or definition, FH-TDMA and FH-CDMA are identical. It seems far less confusing to use CDMA to mean only DS-CDMA and TDMA to mean
into which a DECT carrier with a data rate of 1.152 Mbps is inserted. Radio channels are spaced 2 MHz apart. Because the data rate is significantly lower than the bandwidth, DECT allows adjacent channels to be used in the same cells, unlike most other radio standards. However, it also makes relatively inefficient use of the bandwidth available. Each 1.152-Mbps bearer is divided into 24 timeslots. Nominally, 12 timeslots are for base station-to-subscriber transmission, and 12 are for