- any other use of the work is strictly prohibited. - Short-term Variations of the Signal 41. - Overview of the UE-UTRAN Protocols 256. - Overview of the Concepts 300. - Johnson of the United States and Oki of Japan.. - (1-1) In terms of the radius of a cell R. - The parameters of the table will be discussed later.. - A chronology of the important developments is presented in Table 1-6. - 1991 GSM introduced in Europe and other countries of the world.. - MacDonald, “The Cellular Concept,” Bell Syst. - There are other effects due to the motion of the vehicle. - the width of the streets traversed by the mobiles. - This trend in the signal variation as a function of the base station antenna height is almost independent of the frequency.. - Table 2-1 Values of exponent n in the expression for the received signal as a function of the frequency. - Variation of the Local Mean Signal Level. - where m is the average value of the variable x and s 2 is the variance. - Then typical signal varia- tions as a function of the distance are shown in Figure 2-4.. - Short-term Variations of the Signal. - The power spectral density S(v) of the received signal envelope is given by. - 9 In other words, v d is the maximum apparent change in the frequency of the received signal due to the Doppler effect.. - The direction of the incoming signal with respect to the vehicle velocity. - (b) The power spectrum of the signal envelope received at the antenna of a moving vehicle.. - As indicated before, E rms is the RMS value of the signal envelope. - Hence, the signal is in a fade approxi- mately three percent of the time. - The variation of the sig- Chapter 2. - These profiles are generally not smooth functions of the delay variations. - where t av is the average value of the delay spread. - A block diagram of the simulation model is shown in Figure 2-11.. - Figure 2-11 A simulation model of the Rayleigh fading channel.. - Here V is the vehicle speed, and l is wavelength of the carrier frequency.. - Figure 2-12 The frequency response of the Doppler shaping filter. - The chapter begins with an overview of the various access technologies.. - Pulse-shaping filtering of the incoming data is usually done at the base band. - The clock rate of the spreading code is known as the chip rate. - The ratio of the chip rate to the data rate is called the spreading factor. - The received signal at the input of the demodulator is composed of signals from multiple users.. - composed of the transmitted signals from multiple users.. - The decoder reads the output of the integrator and Chapter 3. - be reset (that is, its output must be dumped) so that the process can recommence at the start of the next symbol period.. - The same is true of the third and following terms.. - However, the output of the integrator due to the first term, when averaged over a symbol period, is s 1 (t) because. - the greater the process gain, the larger the capacity N of the system.. - A simplified block diagram of the transmit functions of a base. - Each of these subsequences is transmitted over a separate CDMA carrier as shown in the lower half of the diagram. - Figure 3-6(a) shows the block diagram of the encoder. - At 12.2 kb/s, a 20 ms frame at the output of the encoder Chapter 3. - Figure 3-6(b) shows the block diagram of the ACELP decoder at the receiving end. - The constraint length of the coder is equal to the length of the registers. - The two generating functions of the code of Figure 3-7(a) are. - Figure 3-8 shows the states of the encoder of Figure 3-7a. - In general, this repetition period is equal to the constraint length of the encoder. - Appendix A provides a brief description of the Viterbi algorithm. - The implemen- tation of the coder of rate 1 / 2 is shown in Figure 3-10. - The output of the interleaver is then applied to the second encoder.. - The phase of the carrier is altered according to the symbol. - Then at instant t 0, the output of the adder is 0. - The output may be taken from any one of the four registers. - Each period of the output sequence contains runs of different lengths. - The output of the demodulator is low-pass filtered, and then applied to the input of a matched filter. - Assuming that the symbol transmitted is 0, the output of the matched filter is in the range. - Soft decision decoding improves the bit error rate performance of the receiver. - Figure 3-21 Four-level quantization of the input to the decision circuit. - Each branch of the receiver is called a finger.. - The output of the channel model is subtracted from the received input. - of the matched filter is decoded in a decision circuit. - This spacing is usually one half of the carrier wavelength.. - This is easily done by adding two 0’s (m 1 0’s in a general case) to the end of the information sequence at the encoder input.. - More specifically, the absolute phase angle of the carrier corresponding to the n-th symbol is given by. - In the previous definition, each modulating symbol was transmitted using an absolute phase of the carrier. - Figure 3-34 The phase transitions of the carrier frequency in QPSK modulation. - For a detailed mathematical analysis of the subject, see references [21]-[24].. - of the two PN codes y 1 (t) and y 2 (t) is given by. - (C-3) Similarly, the output of the matched filter for user 2 is:. - of the trellis is given by values of the cross-correlation functions.. - Abramson, “The Throughput of Packet Broadcasting Channels,” IEEE Trans. - Forney, “The Viterbi Algorithm,” Proc. - In the uplink, there are two physical channels—the access channel and traffic channel. - The transmit functions of the reverse access channel are slightly different. - The output of the channel encoder is repeated once so that the resulting bit rate is 4.8 kb/s. - 2 The symbol rate of the interleaver output on a traffic channel is 19,200 symbols/s.. - it to the target base station as part of the process to drop it from the soft handoff.. - Abram- son, “The Throughput of Packet Broadcasting Channels,” IEEE Trans. - The link layer consists of the link access control (LAC) and media access control (MAC) layers. - Some of the differences are as follows.. - cdma2000 has two traffic channel types—the fundamental and secondary. - It also requires the ser- vices of the AC, which is connected to the HLR. - A brief description of the system is presented here. - A 20 ms frame at the output of the channel encoder contains 456 bits.. - Notice that the data rate at the output of the interleaver is the same as the input.. - The output of the interleaver feeds into the modulator. - The output of the encoder consists of three components: (i) the STP coefficients, also known as the reflection coefficients, (ii) the quantized long-term residual excitation, and (iii) the LTP coeffi- cients. - Figure 5-5 A simplified block diagram of the RPE-LTP speech encoder. - Thirty-two bits are then removed from the output of the encoder. - Similarly, the phase of the carrier also changes in discrete steps. - (5-4) The frequency response of the Gaussian filter has a sharp cutoff.. - After the assignment of the traffic channel, SDCCH must be relinquished.. - There are two channels of this type—the slow and the fast. - Another function of the SGSN is to control user access to the network by. - The packet structure at each layer of the Um interface is shown in Figure 5-16. - The maximum size of the LLC data unit is 1,600 octets
Xem thử không khả dụng, vui lòng xem tại trang nguồn hoặc xem
Tóm tắt