WIRELESS TECHNOLOGYProtocols, Standards, and Techniques pdf phần 6 pot

P1: FDJ book CRC-Wireless November 8, 2001 16:35 Char Count= 327 discontinued and a new communication with a new base station and nec- essarily through an analog channel is established. 5.16.2 Handoff and Pilot Sets The monitoring of pilot channels is decisive in the handoff process. Within a given CDMA frequency assignment, the mobile searches for pilots to detect CDMA channels. Each pilot is associated with the forward traffic channels in the respective forward CDMA channel. A pilot with sufficient signal strength and not associated with any of the forward traffic channels assigned to the mobile station, when detected by it, causes the mobile station to send a pilot strength measurement message to the base station. The base station, in turn, can direct the mobile station to perform a handoff. There are four sets of pilots over which the searches are carried out: active set, candidate set, neighbor set, and remaining set. The active set contains the pilots (as many as six pilots) associated with the forward traffic channels currently assigned to the mobile station. The candi- date set contains the pilots (as many as five pilots) that are not in the active set, but have sufficient strength to permit successful demodulation of the forward traffic channels associated with it. The neighbor set contains the pilots (at least 20 pilots) that are neither in the active set nor in the candidate set but are likely to be candidates to be moved to one of these sets. The remaining set contains all the pilots in the system that are not currently in any one of the other sets. 5.16.3 Handoff Parameters As can be inferred, the pilots play a very important role in the entire handoff process. The search for pilots to detect the presence of CDMA channels to establish the various pilot sets is first step in the handoff process. For each pilot set a search window (range of PN offsets) is specified by the base station. Within the search window, which is centered at the earliest-arriving usable multipath component of the pilot, the mobile station searches for usable mul- tipath components, those the mobile station can employ for the demodulation of the associated forward traffic channels. The window sizes are specified in the system parameters message in the fields to be described next. For pilots within both the active set and candidate set the search window is in the SRCH WIN A field. For pilots within the neighbor set the window size information is conveyed in the SRCH WIN N field. And for the remaining set the window size in given in the SRCH WIN R field. There are 16 possible window sizes, numbered from 0 to 15. The window size fields convey one of these numbers. The actual window size, given in PN chips, as a function of these numbers, is shown in Table 5.1. Note that Table 5.1 gives the total window size, such that, because the search window is centered at the earliest- arriving usable pilot component, the search is carried out within the range ±PN chips/2. The window size should be set according to the propagation © 2002 by CRC Press LLC E:\Java for Engineers\VP Publication\Java for Engineers.vp Thursday, April 25, 2002 9:27:36 AM Color profile: Disabled Composite Default screen P1: FDJ book CRC-Wireless November 8, 2001 16:35 Char Count= 327 TABLE 5.1 Search Window Sizes SRCH WIN A SRCH WIN A SRCH WIN N Window Size SRCH WIN N Window Size SRCH WIN R (PN Chips) SRCH WIN R (PN Chips) 04860 16980 2 8 10 100 3 10 11 130 4 14 12 160 5 20 13 226 6 28 14 320 7 40 15 452 conditions. It should be large enough to detect all usable multipaths and as small as possible to speed the search process. According to the ratio between the pilot energy per chip E c and the to- tal received spectral density I 0 (noise and signals) accumulated within the search windows for each pilot in the pilot sets, these pilots will move from one set to another. Actions concerning the handoff process are taken, based on the parameters specified in the fields T ADD (pilot detection threshold), T DROP (pilot drop threshold), T COMP (comparison threshold), T TDROP (drop timer value) of some messages. T ADD, T DROP, and T COMP are related to signal strength, and T TDROP is associated with the time the sig- nal remains under a certain level. T ADD and T DROP are given in units of −0.5dBE c /I 0 ; i.e., the threshold value is given by −0.5 × T ADD. T COMP is given in units of 0.5 dB; i.e., the threshold is given by 0 .5 × T COMP. T TDROP refers to an expiration time of a timer whose enabling is triggered whenever the strength of any pilot in the active set or in the candidate set drops below the value in T DROP. The timer is considered expired within 10% of the ex- piration time values shown in Table 5.2. A handoff drop timer is maintained TABLE 5.2 Handoff Expiration Time Drop Timer Expiration Drop Timer Expiration Value Time (s) Value Time(s) 0 0.1 8 27 11 939 221055 341179 4612112 5913159 6 13 14 225 7 19 15 319 © 2002 by CRC Press LLC E:\Java for Engineers\VP Publication\Java for Engineers.vp Thursday, April 25, 2002 9:27:36 AM Color profile: Disabled Composite Default screen P1: FDJ book CRC-Wireless November 8, 2001 16:35 Char Count= 327 for each pilot in the active set and in the candidate set. These parameters are further explained later in this section. 5.16.4 Handoff Messages Five messages running on the forward traffic channel and two on the reverse traffic channel are associated with the handoff process. For the forward traffic channel: r Pilot Measurement Request Order r Handoff Direction Message r Analog Handoff Direction Message r Neighbor List Update Message r Extended Handoff Direction Message For the reverse traffic channel: r Pilot Strength Measurement Message r Handoff Completion Message The pilot measurement request order, sent by the base station, causes the mobile station to send, within a certain time (0.2 s), a pilot measurement message. The handoff direction message, sent by the base station, causes the mobile station to update the active set, the candidate set, and the neighbor set. It also causes the mobile station to discontinue the forward traffic channels not associated with pilots not listed in the message, to change the frame offset as specified in the message, and to use the long code mask as specified in the message. The mobile station may encrypt some fields of the message if specified, and perform soft handoff or CDMA to CDMA hard handoff as re- quired. It also stores the values of the fields SRCH WIN A, T ADD, T DROP, T COMP, T TDROP. The analog handoff direction message, sent by the base station, directs the mobile to perform a CDMA to analog handoff. If the mobile station has narrow analog capability (channel with one third of the conventional analog channel), a narrow analog channel may be specified. The neighbor list updated message, sent by the base station, causes the mobile station to update the neighbor set with the pilots specified in the message. If the addition of a pilot to the set exceeds its maximum capacity, the pilots remaining longer in the set are replaced. The extended handoff direction message, sent by the base station, causes the mobile station to perform actions as for the handoff direction message case. © 2002 by CRC Press LLC E:\Java for Engineers\VP Publication\Java for Engineers.vp Thursday, April 25, 2002 9:27:36 AM Color profile: Disabled Composite Default screen P1: FDJ book CRC-Wireless November 8, 2001 16:35 Char Count= 327 In contrast to the handoff direction message, the extended handoff direction message includes the HARD INCLUDED field, which indicates whether or not the mobile station should change the parameters relative to the hard handoff (FRAME OFFSET, PRIVATE LCM, ENCRYPT MODE, NOM PWR, BAND CLASS, CDMA FREQ). The pilot strength measurement message is sent by the mobile station in two situations: (1) as a response to the pilot measurement request order or (2) autonomously, which requires acknowledgment. The autonomous trans- mission of such a message is triggered by the following events: r The strength of a pilot in the neighbor set or in the remaining set is found to exceed the value in T ADD. r The strength of a pilot in the candidate set exceeds that of a pilot in the active set by 0.5 × T COMP dB and a pilot strength measure- ment message conveying such information has not been sent since the last arrival of the handoff direction message or the extended handoff direction message. r The handoff drop timer of a pilot in the active set has expired and a pilot strength measurement message conveying such information has not been sent since the last arrival of the handoff direction message or the extended handoff direction message. The handoff completion message is sent by the mobile station as a response to the handoff direction message or extended handoff direction message, i.e., after the actions required by these messages have been completed. 5.16.5 Pilot Sets Updating The updating of the various pilot sets is triggered by a series of events as summarized next. Active Set. The active set, with a maximum size of six pilots, is initialized when the mobile station is first assigned a forward traffic channel, in which case it shall contain only the pilot associated with the assigned channel. The reception of the handoff direction message or of the extended handoff direc- tion message triggers the mobile station to replace the pilots in the active set with those listed in the message. All pilots in the active set have their strength continuously monitored by the mobile station. Candidate Set. The candidate set, with a maximum size of five pilots, is initialized to contain no pilots. The update of the candidate set occurs as follows. r A pilot is moved from the neighbor set or from the remaining set to the candidate set if the strength of this pilot exceeds T ADD. © 2002 by CRC Press LLC E:\Java for Engineers\VP Publication\Java for Engineers.vp Thursday, April 25, 2002 9:27:36 AM Color profile: Disabled Composite Default screen P1: FDJ book CRC-Wireless November 8, 2001 16:35 Char Count= 327 r A pilot from the active set is added to the candidate set if the re- ceived handoff direction message or extended handoff direction mes- sage does not contain that pilot and its handoff drop timer has not expired. r A pilot is moved from the candidate set to the active set if the received handoff direction message or extended handoff direction message contains that pilot. r A pilot is moved from the candidate set to the neighbor set if its handoff drop timer expires. r A pilot is removed from the candidate set if, by adding another pilot in the candidate set, its maximum size is exceeded. In such a case, the pilot chosen to be deleted is the one with its handoff drop timer closest to the expiration time. If more than one pilot is found in this condition or if no pilot has its handoff drop timer enabled, then the pilot with the lowest strength is deleted. Neighbor Set. The neighbor set, with a minimum size of 20 pilots, is ini- tialized to contain all the pilots specified in the last-received neighbor list message when the mobile is first assigned a forward traffic channel. An aging mechanism is employed by the mobile station to keep in the set those pilots that were most recently detected. In addition to the aging mechanism, the update of the neighbor set occurs as follows. r A pilot from the candidate set is addedto the neighbor set if its handoff drop timer expires. r A pilot from the active set is added to the neighbor set if the received handoff direction message or extended handoff direction message does not contain that pilot and its handoff drop timer has not expired. r A pilot from the candidate set is added to the neighbor set if this pilot has been deleted from the candidate set because the number of pilots in this set has exceeded its maximum allowable number at the candidate set updating process. r A pilot is deleted from the neighbor set if its strength exceeds T ADD. r A pilot is deleted from the neighbor set if the received handoff di- rection message or extended handoff direction message contains that pilot. r A pilot is removed from the neighbor set if, by adding another pilot in the neighbor set, its maximum size is exceeded. In this case, the pilot chosen to be deleted is the one that has remained longer in the set. If more than one pilot is found in this condition, then the pilot with the lowest strength is deleted. © 2002 by CRC Press LLC E:\Java for Engineers\VP Publication\Java for Engineers.vp Thursday, April 25, 2002 9:27:36 AM Color profile: Disabled Composite Default screen P1: FDJ book CRC-Wireless November 8, 2001 16:35 Char Count= 327 5.17 Power Control To achieve the best performance, CDMA technology requires equalization of the signal strengths of the mobile station arriving at the base station. Ideally, because the forward link operates coherently, only the reverse link, which operates incoherently, requires power control. The near–far phenomenon ef- fect is more relevant in multipoint-to-point transmission (mobile stations to base station) than in point-to-multipoint transmission. In the first case (multipoint-to-point), because the mobile stations may be at different dis- tances from the base the various signals arriving at the base will have dif- ferent strengths: at the base station, the signal strength of a mobile station near a base station is equivalent to a number of mobile stations away from the base station. Therefore, if no power control is exercised, the near–far phe- nomenon will drastically affect system capacity. In the second case (point- to-multipoint), and in theory, the various signals transmitted by the base will reach a given mobile station with the same power loss, thus maintain- ing power proportionality. In practice, however, both reverse link and for- ward link require power control, the reverse link for the reasons already outlined, and the forward link to compensate for poor reception conditions encountered by the mobile station. TIA/EIA/IS-95 specifies detailed power control algorithms for the reverse link. For the forward link, on the other hand, only an exchange of information between base station and mobile station is stipulated; specific procedures, however, are left to individual implementations. 5.17.1 Reverse-Link Power Control Two independent means of reverse-link power control are specified by the TIA/EIA/IS-95 standard: open-loop power control and closed-loop power control. Open-loop power control is so called because it is a purely mobile-controlled operation (the base station is not involved). The power adjustment is based on the pilot signal level measured at the mobile station: the larger the received power at the terminal, suggesting proximity between base station and mo- bile station, the smaller the transmitted power from the terminal, and vice versa. Additional open-loop operation adjustments are carried out as the mo- bile station attempts to transmit on the access channel in the process known as probing. As already explained in this chapter, each probe on the access channel is carried out at increasing power levels until successful access is accomplished. The initial transmission on the reverse traffic channel, there- fore, accumulates the additional power due to the access probes. Note that © 2002 by CRC Press LLC E:\Java for Engineers\VP Publication\Java for Engineers.vp Thursday, April 25, 2002 9:27:36 AM Color profile: Disabled Composite Default screen P1: FDJ book CRC-Wireless November 8, 2001 16:35 Char Count= 327 open-loop power control assumes reciprocity between reverse link and for- ward link, i.e., it assumes that both links experience correlated fading. Closed-loop power control is so called because it involves both base sta- tion and mobile station in the power adjustment process. By monitoring the reverse-link quality,the base station commands the mobile station to adjust its output power to achieve the desired grade of service. The command is given through the power control bits (PCBs) sent over the forward traffic channel, as explained previously. Closed-loop power control encompasses an inner loop control and an outer loop control. Only inner loop power control is spec- ified by EIA/TIA/IS-95. In inner loop control, the commands to increase or to diminish the output power of the mobile station are given based on the fact that a given ratio of energy per bit and total noise density, E b /N o , has been established as the threshold for the required performance. In outer loop con- trol, the E b /N o level is adjusted to give the minimum acceptable frame error rate (FER). Therefore, the output of the outer loop control process constitutes the input for the inner loop control process, with both processes interacting dynamically to give the minimum output power of the mobile station for a minimum E b /N o to yield the desired FER. Because of the large frequency separation between forward channels and reverse channels, forward and reverse links fade independently. Therefore, for an efficient power control mechanism, both open-loop power control and closed-loop power control must interact. Open-loop power control may be considered coarse-tuning and closed-loop power control fine-tuning of the overall reverse-link power adjustment process. The temporal response of the mobile station to open-loop control is inten- tionally made nonlinear. If the mobile station perceives a sudden increase of the signal strength of a pilot, it immediately (within microseconds) responds with a proportionally reduced output power. However, if the opposite oc- curs (a sudden decrease in received signal strength), it responds with a slow (within milliseconds) but proportional increase of its output power. The ra- tionale for this lies in the fact that, apart from fading, a higher received power is a better estimate of the average link loss. In addition, if an improvement in the radio path is found, a decrease of the output power of the mobile station is imperious, so that undue interference and consequent decrease in capacity are avoided. In the same way, a sudden worsening of the radio path followed by an immediate increase of the output power of the mobile station may cause undue interference, and consequent decrease in capacity, because such awors- ening may be due to fading occurring only on the forward link. Note that this rule benefits the whole system performance to the detriment of the single user. Regarding closed-loop power control, the temporal response of the mobile station is immediate. The 800-bit/s PCB rate implies that once at each 1.25 ms an action is taken with respect to the output power of the mobile station. A 0 in PCB causes a 1-dB increase and a 1 causes a 1-dB decrease in the overall power © 2002 by CRC Press LLC E:\Java for Engineers\VP Publication\Java for Engineers.vp Thursday, April 25, 2002 9:27:36 AM Color profile: Disabled Composite Default screen P1: FDJ book CRC-Wireless November 8, 2001 16:35 Char Count= 327 output. During soft handoff, however, there may be conflicting commands with different base stations involved in the handoff instructing the mobile station to act differently. The mobile station will power up if all the base stations involved in the handoff command it to do so; if at least one base station commands a power-down, a power-down shall be done. The overall power control formula is given by mean output power = constant + open loop adjustment + closed loop adjustment (dBm) (5.4) The parameters considered in the Equation 5.4 are specified in the access parameters message and are obtained by the mobile station prior to trans- mitting. The constant in Equation 5.4 is given by the sum of the values of NOM PWR (−8dB ≤ NOM PWR ≤ 7 dB, nominally 0 dB), INIT PWR (−16 dB ≤ INIT PWR ≤ 15 dB, nominally 0 dB), and −73. The figure −73 is obtained as follows. [1] The link budget equation, in decibels, for the reverse link can be simplistically written as base received SNR = mobile transmitted power − propagation losses − reverse noise and interference (5.5) For the forward link: mobile received SNR = base transmitted power − propagation losses − forward noise and interference (5.6) Assuming that the propagation losses are the same for forward and reverse links, then manipulating Equations 5.5 and 5.6 leads to mobile transmitted power = (base received SNR + forward and reverse noise and interference + base transmitted power) − mobile received power (5.7) For base-received SNR = −13 dB, forward and reverse noise and interference = −100dBm, and base transmitted power = 40 dBm (10 W), the terms between parentheses in Equation 5.7 yield −73 dBm. NOM PWR is the adjustment to give the correct received power at the base station if INIT PWR is 0 dB. And INIT PWR provides the adjustment to the first access channel probe with the aim of providing at the base station a received power somewhat less than the required signal power, which is a conservative measure to compensate for the partially decorrelated path losses © 2002 by CRC Press LLC E:\Java for Engineers\VP Publication\Java for Engineers.vp Thursday, April 25, 2002 9:27:36 AM Color profile: Disabled Composite Default screen P1: FDJ book CRC-Wireless November 8, 2001 16:35 Char Count= 327 between forward and reverse links. The open-loop adjustment in Equation 5.4 is given by the sum of the mean input power and the accumulated increase in power due to the channel access probes. The increase power step is given in PWR STEP (0 dB ≤ PWR STEP ≤ 7 dB). If n channel access probes are carried out, then (n − 1) ×PWR STEP is the total power increase at the end of the sequence. The closed-loop adjustment in Equation 5.4 is given by the net value of the increase and decrease in power given by the PCBs. If n 0 is the number of bits 0 received and n 1 is the number of bits 1 received in the PCBs, then the mentioned net value is (n 0 −n 1 ). The final open-loop and closed-loop equation is mean output power = −73 + NOM PWR + INIT PWR −mean input power + (n − 1)PWR STEP +(n 0 − n 1 ) (dBm) (5.8) 5.17.2 Forward-Link Power Control As mentioned previously, specific procedures for forward-link power control algorithms are not defined by EIA/TIA/IS-95. And these are left to individual implementations. Some directions, on the other hand, are to be followed. They vary for the Rate Set 1 (9.6, 4.8, 2.4, and 1.2 kbit/s) and for the Rate Set 2 (14.4, 7.2, 3.6, and 1.8 kbit/s) configurations. For both configurations, the quality of the reverse link is monitored by the mobile station and its condition is reported back to the base station. In particular, for the Rate Set 1 the quality of the forward link is assessed by its FER. The FER is then reported to the base station in the power measurement report message either periodically (at each 250 ms or less) or if it exceeds a certain threshold. Based on this report, the base station increases its power by a certain amount, nominally 0.5 dB, limited to ±6 dB about the nominal power. For the Rate Set 2, the forward-link quality is assessed by means of the occurrence of a frame erasure. A frame erasure causes the mobile station to appropriately set an erasure indicator bit in the corresponding frame of the reverse link for the pertinent action by the base station. Note that the power tracking performance of the Rate Set 2 configuration (once at each 20 ms, the duration of a frame) is much faster than that of the Rate Set 1 configuration. 5.18 Call Procedures This section illustrates some simplified call procedures. Here, the abbrevia- tions MS, for Mobile Station, and BS, for Base Station, are used. © 2002 by CRC Press LLC E:\Java for Engineers\VP Publication\Java for Engineers.vp Thursday, April 25, 2002 9:27:36 AM Color profile: Disabled Composite Default screen P1: FDJ book CRC-Wireless November 8, 2001 16:35 Char Count= 327 5.18.1 Mobile Station Origination The following sequence of events occurs in an MS call origination. 1. MS detects user-originated call. 2. MS sends the origination message, using the access channel and the access procedure. 3. BS detects the origination message and performs the authentication verification process. (The steps concerning the authentication pro- cedure are not detailed here.) BS sets up the forward traffic channel. 4. BS sends an acknowledgment order on the paging channel. 5. BS sends a sequence of 1s and 0s (the null traffic channel data) on the designated forward traffic channel. 6. BS sends the channel assignmentmessage containing the channel in- formation (ESN, code channel, CDMA frequency assignment, frame offset). This is carried out on the paging channel. 7. MS detects the channel assignment message. It tunes to the assigned forward traffic channel and detects the null traffic channel data. 8. MS sends the traffic channel preamble using the reverse traffic channel. 9. BS receives the traffic channel preamble. It then sends an acknow- ledgment order using the forward traffic channel. 10. MS detects the acknowledgment order. It then sends the null traffic channel data using the forward traffic channel. 11. BS detects the null data and sends the service connect message using the forward traffic channel. 12. MS receives the service connect message. If the MS can fulfill the service requirements specified in this message, it then sends a serv- ice connect completion message using the forward traffic channel. 13. BS detects the service connect completion message and sends the alert with information message using the forward traffic channel. This message contains information on the ring-back tone. 14. MS detects the alert with information message and applies the ring- back tone, as required. 15. BS is informed about the off-hook condition of the called party. It sends the alert with information message on forward traffic channel. This message commands the ring-back tone off. 16. MS detects the alert with information message and removes the ring-back tone. 17. Bidirectional conversation begins. © 2002 by CRC Press LLC E:\Java for Engineers\VP Publication\Java for Engineers.vp Thursday, April 25, 2002 9:27:36 AM Color profile: Disabled Composite Default screen [...]... 15 4 6 8 10 12 14 16 1 2 3 4 5 6 7 © 2002 by CRC Press LLC E:\Java for Engineers\VP Publication\Java for Engineers.vp Thursday, April 25, 2002 9:27: 36 AM Rate Set 1 (kbit/s) Rate Set 2 (kbit/s) 1.2, 2.4 4.8, 9 .6 19.2 28.8 38.4 48.0 57 .6 67.2 76. 8 1.8, 3 .6 7.2, 14.4 28.8 43.2 57 .6 72.0 86. 4 100.8 115.2 Color profile: Disabled Default screen Composite P1: FDJ book CRC -Wireless November 8, 2001 16: 35... 9:27: 36 AM Color profile: Disabled Default screen Composite P1: FDJ book CRC -Wireless November 8, 2001 16: 4 Char Count= 303 Part III Wireless Data © 2002 by CRC Press LLC E:\Java for Engineers\VP Publication\Java for Engineers.vp Thursday, April 25, 2002 9:27: 36 AM Color profile: Disabled Default screen Composite P1: FDJ book CRC -Wireless November 8, 2001 16: 4 Char Count= 303 6 Wireless Data Technology 6. 1... control messages; coding, encapsulation, and transmission processes © 2002 by CRC Press LLC E:\Java for Engineers\VP Publication\Java for Engineers.vp Thursday, April 25, 2002 9:27: 36 AM Color profile: Disabled Default screen Composite P1: FDJ book CRC -Wireless November 8, 2001 16: 4 Char Count= 303 TDMA frame Time Slot Number 01234 567 01234 567 01234 567 01234 567 01234 567 01234 567 0123 PDCH 7 PDCH 0 radio blocks... soft handoff criteria render the system more flexible with the thresholds for inclusion and removal of pilots set dynamically Therefore, unnecessary handoffs are avoided leading to an increase in the system capacity 5.19.4 Hard Handoff The hard handoff process here concerns the D-to-D handoff, in which a handoff between CDMA carriers occurs In EIA/TIA/IS-95A, a D-to-D handoff is carried out via the handoff... current pilot set lists is saved, the D-to-D handoff is tried, and if it is not successful the saved configuration is restored and no handoff is performed 5.19.5 Idle Handoff EIA/TIA/IS-95B allows the execution of idle handoffs in situations not permitted by EIA/TIA/IS-95A These situations concern the access procedures, as follows: Access Handoff Access handoff may occur in two situations: while the... for Engineers.vp Thursday, April 25, 2002 9:27: 36 AM Color profile: Disabled Default screen Composite P1: FDJ book CRC -Wireless November 8, 2001 Application 16: 4 PDU (arbitrary size) TCP / IP PDU SNDCP PDU LLC PDU Char Count= 303 (64 k-octects) (1. 56 k-octects) TCP / IP SNDCP (1.5 56 k-octects) MAC / RLC PDU (20-50 octects) MAC / FIGURE 6. 3 Segmentation and encapsulation in GPRS (the figures in parentheses... PDU Figure 6. 4 shows the radio block structures for user data and control messages It also illustrates the coding, encapsulation, and transmission processes In Figure 6. 4, the numbers indicate the bits in each field Table 6. 1 shows the GPRS coding schemes and the respective throughput rate As already mentioned, GPRS employs the same frame structure as GSM Each frame has a duration of 4 .61 5 ms and consists... puncturing Radio Block 4 56 segmentation 114 114 114 114 encapsulation Time slot x, Frame y 1 56. 25 T DATA 3 57 Time slot x, Frame y+1 1 56. 25 F TRAIN F DATA 1 26 1 57 Time slot x, Frame y+2 Time slot x, Frame y+3 1 56. 25 1 56. 25 T GUARD 3 8.25 Normal BURST T: Tail bits F: Stealing flag DATA: Data bits TRAIN: Training bits GUARD: Guard bits FIGURE 6. 4 GPRS radio block structures: user data and control messages;... data rate transmissions, soft handoff algorithms, and power control techniques have been introduced References 1 Lee, J S and Miller, L E., CDMA Systems Engineering Handbook, Artech House, Boston, 1998 2 Mobile Station–Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System (TIA/EIA-95-A), 1995 3 Mobile Station–Base Station Compatibility Standard for Dual-Mode Spread... the CDMA candidate carrier 2 Candidate Frequency Search Set, which is a list containing the pilots of the CDMA candidate carrier to be searched under the command of the base station © 2002 by CRC Press LLC E:\Java for Engineers\VP Publication\Java for Engineers.vp Thursday, April 25, 2002 9:27: 36 AM Color profile: Disabled Default screen Composite P1: FDJ book CRC -Wireless November 8, 2001 16: 35 Char . (kbit/s) 12 0 1.2, 2.4 4.8, 9 .6 1.8, 3 .6 7.2, 14.4 3 4 1 19.2 28.8 5 6 2 28.8 43.2 7 8 3 38.4 57 .6 9 10 4 48.0 72.0 11 12 5 57 .6 86. 4 13 14 6 67.2 100.8 15 16 7 76. 8 115.2 © 2002 by CRC Press. CRC -Wireless November 8, 2001 16: 35 Char Count= 327 discontinued and a new communication with a new base station and nec- essarily through an analog channel is established. 5. 16. 2 Handoff and. FDJ book CRC -Wireless November 8, 2001 16: 35 Char Count= 327 for each pilot in the active set and in the candidate set. These parameters are further explained later in this section. 5. 16. 4 Handoff