Литература / UMTS-Report

3.2.1.1 Macro cellular environment with bad Eb/N0 conditions

puncturing (2 + 3.x) bits

448 bits

modulator (QPSK) 224 symbols

interleaver

FRAME 0 FRAME 1 FRAME 2 FRAME 3

28 28

symbols symbols

Figure 3.1 Speech service mapping for macro cellular environments with bad Eb/N0 conditions

The speech service mapping for macro cellular environments with bad Eb/N0 conditions is depicted in Figure 3.1. This mapping is used in large macro cells, like in rural areas. 64 speech channels are provided per carrier. By using a channel coding rate of R = 1/3, a very low Eb/N0 is required to achieve the QoS requirements.

First, the data from layer 2 (150 bits + x bits L2 overhead) are encoded with code rate Rc = 1/3. Then 2 bit + 3x bit are punctured to get an output block size of 448 encoded bits. These 448 encoded bits are mapped onto 224 QPSK symbols. These 224 QPSK symbols are then interleaved and distributed over four TDMA frames. In each used frame, only one slot and one code is used to transmit 56 symbols per frame making up a total number of 4 basic physical channels.

3.2.1.2 Macro cellular environment with better Eb/N0 conditions

puncturing (226 + 3.x) bits

224 bits

modulator (QPSK) 112 symbols

interleaver

FRAME 0 FRAME 1 FRAME 2 FRAME 3

28 28

symbols symbols

Figure 3.2 Speech service for macro cellular environment with better Eb/N0 conditions

For better Eb/N0 conditions, a higher code rate of approx. Rc = 2/3 can be used. As in macro cellular environments with bad Eb/N0 conditions, the spread speech/data burst 1 is deployed. In Figure 3.2, the mapping for macro cellular environments with normal Eb/N0 conditions is depicted. By using this mapping, 128 speech channels of 8kbit/s can be provided on each carrier. This mapping is used in small macro cells with high traffic density like in urban environments.

First, the data from layer 2 is encoded with rate Rc = 1/3. After puncturing (226 + 3x) encoded bits, 224 encoded bits are passed on to the bit to symbol mapper which generates 112 QPSK symbols. The

interleaver distributes the 112 QPSK symbols over two out of four frames. Hence, only 2 basic physical channels are utilized.

3.2.1.3 Micro and pico cellular environments

puncturing (178 + 3.x) bits

272 bits

modulator (QPSK) 136 symbols

interleaver

FRAME 0 FRAME 1 FRAME 2 FRAME 3

34 34

symbols symbols

Figure 3.3 Speech service mapping for micro and pico cellular environments

In micro and pico cellular environments, the spread speech/data burst 2 with 68 symbols per time slot and code can be used. In Figure 3.3, the mapping for these environments is shown.

The data from layer 2 is encoded with code rate Rc = 1/3. After puncturing (178 + 3x) encoded bits, 272 encoded bits are passed on to the bit to symbol mapper which generates 136 QPSK symbols. The interleaver distributes the 136 QPSK symbols over two out of four frames. Hence, only 2 basic physical channels are utilized.

3.2.1.4 GSM type speech service

Another possibility of providing speech service is a modified interleaving which allows a better exploitation of time diversity. In what follows, a service will be described which is intended for deployment in macro cellular environments with bad Eb/N0 conditions, cf. Figure 3.4.

Figure 3.4 Speech service mapping for micro and pico cellular environments

64 speech channels are provided per carrier. By using a channel coding rate of Rc = 1/3, a very low Eb/N0 is required to achieve the QoS requirements. The mapping shall be described by considering two consecutive PDU's from layer 2. The PDU's are distinguished by their color inFigure 3.4, the first one being depicted in blue, the second one in red. First, the two PDU's from layer 2, each containing 150 bits + x bits L2 overhead, are encoded with code rate Rc = 1/3. Then, in each PDU, 2 bit + 3x bit are punctured to generate an output block size of 448 encoded bits. These 448 encoded bits are mapped onto 224 QPSK symbols. The 224 QPSK symbols are then interleaved with the same procedure used in GSM.

The mapping of the 224 QPSK symbols per PDU will be described by setting out from the left, i.e. the blue, PDU. In Figure 3.4, the slots available in eight consecutive TDMA frames are explicitly shown. Each TDMA frame consists of eight time slots and eight CDMA codes per time slot. The time slots are distinguished by their allocation with respect to the time axis whereas the CDMA codes are distinguished by their allocation with respect to the code axis. We denote upper left slot per TDMA frame slot 1 and the lower right shall be referred to as slot 64. Without loss of generality, only slot 1 is considered. In each slot, a burst is transmitted consisting of two burst halves comprising 28 QPSK symbols each.

The 224 QPSK symbols are allocated to eight groups of 28 QPSK symbols each. Each group of 28 QPSK symbols is then mapped onto a burst half. The first four groups of 28 QPSK symbols are allocated to the first burst halves of four bursts whereas the second four groups of 28 QPSK symbols are mapped onto the second burst halves. Meanwhile, the first four groups of 28 QPSK symbols associated with the following PDU, depicted in red, are mapped onto the first burst halves of the latter four bursts.

3.3 Mixed services

In the following a set of possible mixed service scenarios will be discussed with respect to a user deploying two different services simultaneously and in regard of the radio network offering a service mix.

Figure 3.5 50% speech + 50% UDD 8 (short UDD 8 packets)

Assume that one Erl is related to a simultaneous connection consisting of speech and UDD 8. In this case, between 32 and 64 Erl can be offered. Thus, a maximum of 64 simultaneous connections are supported per cell and carrier. This is also the case when each user simultaneously entertains a speech and a UDD 8 connection.

Assume that a user only uses one type of service, be it speech or UDD 8. In this case between 32 and 64 speech users can coexist with between 32 and 64 UDD 8 users.

Figure 3.5 shows one possibility of implementing the services for the case of short UDD 8 packets containing 150 bits each. The service mix is based on the speech service described in Figure 3.2. The short UDD 8 service uses a block size of 150 bits and a coding rate of 1/3. After additition of the layer 2 overhead and puncturing the 448 bits are mapped onto 224 symbols interleaved and distributed over 4 TDMA frames. The mapping of the speech and the UDD 8 PDU's is depicted in Figure 3.5 over four successive TDMA frames. For the purpose of distinguishing the two types of PDU's, the speech PDU is shown in blue color whereas the UDD 8 PDU is red.

The speech service only requires two slots out of the 4N64 = 256 slots available in the four TDMA frames. Assume that within each TDMA frame slot #1 is located in the upper left edge, slot #8 is located in the lower left edge, cf. Figure 3.5. To allow the exploitation of time diversity, only slots of every second TDMA frame are used for this speech service. Without loss of generality, slot #8 of TDMA frame 1 and 3 are used for the speech service.

The chosen UDD 8 service requires allocation of a single slot in every consecutive TDMA frame. Without loss of generality, slot #4 of every TDMA frame is used, cf. Figure 3.5.

Hence, only two out of 64 slots of TDMA frames 1 and 3 and only one slot of TDMA frames 2 and 4 are used. All other slots are still available for other services. Hence, 32 Erl of (50% speech + 50% UDD 8) service mix can be supported per carrier as illustrated in Figure 3.5.

In this case, still 32 slots of TDMA frame 2 and 32 slots of TDMA frame 4 are not allocated. These slots could then still be allocated to 32 more users of speech service.

Figure 3.6 50% speech + 50% UDD 8 (long UDD 8 packets)

Figure 3.6 shows another possibility of implementing the services for the case of long UDD 8 packets containing 3600 bits each. The service mix is based on the same speech service and the long UDD 8 service.

The long UDD 8 service uses a block size of 3600 bits and a coding rate of 1/3. After additition of the layer 2 overhead and puncturing the 10752 bits are mapped onto 5376 symbols interleaved and distributed over 96 TDMA frames.

Twenty-four consecutive speech PDU's each containing 150 bits and one UDD 8 PDU with 3600 bits are considered in Figure 3.6. The information contained in all these PDU's is distributed over 96 consecutive TDMA frames. Similar to Figure 3.5, only every second TDMA frame is required for the deployed speech service. Therefore, slot #8 of every odd numbered TDMA frame is used for speech service. To facilitate the UDD 8 service, slot #4 of every consecutive TDMA frame is used.

According to Figure 3.6, 32 Erl of (50% speech + 50% UDD 8) service mix can be supported. Furthermore, 32 slots of every even numbered TDMA frame are unused allowing for the support of e.g. up to 32 Erl of speech service No. 2 of Figure 3.6.

3.3.3 50% speech + 50% UDD 2048

Assume that one Erl is related to a simultaneous connection consisting of speech and UDD 2048. In this case, 1 Erl can be offered per carrier. This is also the case when a user simultaneously entertains a speech and a UDD 2048 connection.

Now, assume that a user only uses one type of service, be it speech or UDD 2048. In this case 1 speech user can coexist with 1 UDD 2048 user.

Figure 3.8 illustrates a possible implementation of the service mix for the case of UDD 2048 packets containing 128N3600 bits each and the same speech service as above. In this case, 1 Erl of (50% speech + 50% UDD 2048) service mix can be supported.

In Figure 3.8, 48 consecutive TDMA frames with 64 slots each are shown. Furthermore, twelve successive speech PDU's of 150 bits each are considered. To implement the speech service a single slot is required every second TDMA frame. Without loss of generality, slot #8 is utilized for speech transmission in each odd numbered TDMA frame.

According to Figure 3.8, slots #9…#64 of every TDMA frame are used for implementing the UDD 2048 service. 128 consecutive UDD 2048 PDU's with 3600 bits each are considered. One possible way of distributing the information contained in these PDU's over the 48 TDMA frames is indicated in

Figure 3.8.

Figure 3.8 50% speech + 50% UDD 2048