Adaptive Multimedia Traffic Multiplexing for Dedicated Channels in the UMTS System

J.R. Gállego, A. Hernández-Solana, M. Canales, A. Valdovinos Communications Technologies Group (GTC). Aragon Institute for Engineering Research (I3A). María de Luna 1, 50018, University of Zaragoza, SPAIN {jrgalleg, anhersol, mcanales, toni}@unizar.es

Abstract WCDMA UMTS environment that considers the different aspects concerning the physical layer, In this paper, a multiservice transmission scheme is functionalities of the UMTS protocol stack and system evaluated for the Dedicated Channel of the Universal capabilities. Errors in the Signal to Interference Ratio Mobile Telecommunications System. The transmission (SIR) estimated by the power control are also rate for each service is determined according to its QoS considered. A new strategy to select transmission rates requirements by means of an adaptive Transport Format of the multiplexed services is proposed and evaluated. selection. The proposed selection is based on buffer This strategy takes into account buffer occupation, delay occupation, delay requirements and target bit rate, requirements and target bit rate keeping power keeping power constraints. This power restriction constraints. UMTS also allows to multiplex different depends on the estimated residual capacity and the services in upper layers (Logical Channels) sharing a contribution of this particular mobile user to the system common transmission rate (Transport Channel). This load. Service multiplexing in upper layers (Logical multiplexing is proposed for video and game Channels) sharing a common transmission rate transmission, and two strategies to share the common (Transport Channel) has been evaluated by means of rate are evaluated. two different dequeueing strategies. The remaining paper is organized as follows. In Section 2, a description of the UMTS system functionalities, services and service capabilities is given 1. Introduction and the proposed strategies are described. In Section 3, One of the key requirements of the UMTS air the system model is presented and main parameters are interface is the support for multiplexing different described. We discuss performance results in Section 4 services with different QoS on a single connection. The and, finally conclusions are provided in Section 5. main advantage of the WCDMA air interface to provide 2. QoS for the UMTS Air Interface these differentiated services is the option of variable transmission data rates through different spreading Provision of QoS in the UMTS air interface is related factors, multicode transmission and coding schemes. to functionalities of the radio interface protocol The acceptance of a new user connection must be architecture, which is shown in Fig. 1. The WCDMA conditioned by the fact that target signal to interference physical layer offers data transmission services to ratio (Eb/No) values can be achieved by each existing Medium Access Control (MAC) layer [1] by means of connection once a new one is activated. Therefore, Transport Channels (TrCh). The set of specific attributes getting the required QoS for each user is closely of the physical layer (channel coding, interleaving, and connected with power allocation. A good interference transmission rate) is referred to as the Transport Format handling by radio resource allocation schemes plays an (TF) of the considered TrCh, and it determines the important role to guarantee the performance and to transmission quality for the data information to be sent. increase the system capacity. When a connection is The MAC entity is responsible for mapping Logical accepted, certain resources are allocated for this user. Channels (LCh) onto TrChs, selection of TF, priority Different services can be multiplexed over this same handling and dynamic scheduling. A set of LCh types is connection with different QoS requirements. According defined for the different kinds of data transfer services to these QoS requirements and the available resources, offered by MAC. They can be dedicated, shared and transmission rates for each multiplexed service must be common channels. A LCh is defined by the type of determined. In this paper, an analysis of service transferred information. Each of the multiplexed LChs multiplexing in the dedicated channel (DTCH) for both may have variable data rate on a TTI (Transmission uplink and downlink is carried out in a realistic Time Interval) by TTI basis. Each combination of rates on the individual channels results in a certain data format PDUs with a lower WT are firstly dequeued. to be transmitted, defining the total number of bits per In order to guarantee QoS in terms of Bit Error Rate frame and their assignment to the individual channels (BER) or Block Error Rate (BLER), a specific bit energy (Transport Format Combination – TFC) [2]. to interference ratio (Eb/No) must be provided for each Mobile Station Base Station RRM Entity User information User information service. A joint symbol energy to interference ratio Mapping QoS according type of service (Es/No) needs to be computed according to the TFC so Call Admission Control according type of service. that all Eb/No are met. Rate matching (RM) [2] provides Resource Allocation PDCP PDCP the required Eb/No for each of the multiplexed services in RLC RLC RLC RLC RLC RLC RLC RLC RLC RLC RRC the CCTrCH. Equations (2) and (3) show the basic

DCCHDTCH DTCH DTCH Logical channels DTCHDTCH DCCH process in the uplink. MUX MAC MAC MUX TFC selection § Ec · DCH DCH Transport channels DCH DCH ¨ N ¸ Ni  ǻNi © 0 ¹i § E · § E · Rb Physical Layer (Hidden Markov Model) , c b (2) ¨ N ¸ ¨ N ¸ ˜ Function (Propagation, mobility, power control accuracy,coding, interference level) Ni Es © 0 ¹i © 0 ¹i Rc N0 Figure 1. UTRA-FDD Radio Interface protocol for i = 1,..., I (number of TrChs) architecture I I § § E c · · E s In addition to physical procedures, upper layers ¨ Ni u ¨ ¸ ¸ Ndata u , Ndata Ni  'Ni (3) ¦¨ N0 ¸ N0 ¦ provide other feasibilities depending on the service i 1© © ¹i ¹ i 1 requirements. In particular, the Radio Link Control where Rb and Rc are transmission rates before and after (RLC) [3] protocol can provide a reliable service channel coding, Ndata is the number of bits transmitted dependent transmission by selecting its operating mode. over the CCTrCH in a frame with rate Rs (bauds), Ni are In fact, UMTS system considers three different modes in the bits associated to each service and 'Ni the added bits RLC configured by the Radio Resource Controller to match the total rate to Rs. RM is similar in both links, (RRC) [4]: based on FEC are Transparent Mode (TM) although the process is less dynamic in the downlink. and Unacknowledged Mode (UM) whereas the Spreading factor is fixed and DTX (Discontinuous Acknowledged Mode (AM) is based on joint FEC and Transmission) is used in addition to repetition and ARQ. The RLC mode also allows the use of early puncturing in order to match the variable transmission discard, which allows to drop in the transmitter packets rate of each service. Power transmission is determined that have exceeded the maximum tolerable delay, by the required Es/No, channel conditions and system reducing the delay of the following packets. The time a interference level in different ways for both links. These packet is allowed to stay in the RLC buffer is controlled dependences are shown in (4) and (5). and signalled by upper layers. We have considered a K ˜W  F  U ˜ P ˜ h P 0 i T BS idown P (4) packet-dependent value according to (1) T BS,i W MAX BS,i U  § Es · Li Rs ˜ ¨ ¸ TDisc,i Tmargin  TTX ,i Tmargin  (1) © N0 ¹ R target where PT-BS,i is the transmitted power by the Base Station where Li is the length of packet i and TTX,i the time to (BS) associated to user i, PMAX-BS,i its maximum allowed transmit packet i at Rtarget, and Tmargin an additional value, and PT-BS the total transmitted power, K0 the provided margin. thermal noise spectral density, W the available Several LChs, belonging to different services (e.g. bandwidth in the cell, Fi the intercell interference video, audio, etc) can be jointly transmitted, using observed by the user i, U the orthogonality factor, and hi- different TrChs (with their corresponding TF) down the path loss between BS and user i. multiplexed over the Coded Composite Transport K0 ˜W (5) Channel (CCTrCH) [2], [4]. Some of the multiplexed PT UE,i PMAX UE,i § · TrChs can also convey several LChs sharing the same ¨ ¸ ¨ W ¸ TrCh attributes. When different LChs are transmitted Cres ˜ hiup ˜ 1  ¨ § Es · ¸ ¨ Rs ˜ ¨ ¸ ¸ over the same TrCh, the MAC entity has to multiplex © © N0 ¹ ¹ upper layer PDUs from the different RLC entities into the where PT-UE,i is the transmitted power by user i, PMAX-UE,i transport block sets delivered to the physical layer. In this is the maximum transmitted power, Cres is the residual paper, two different dequeueing strategies have been capacity in the system, and hi-up is the path loss between implemented in order to evaluate how the multiplexing user i and the BS. The residual capacity is given, on strategy affects the system performance: average, by the expression (6), 1) First In First Out (FIFO): RLC PDUs are mapped onto -1 § · transport blocks in the same order they arrive at the RLC ¨ ¸ N ¨ W ¸ queues, regardless of the LCh they belong to. Cres 1  (1  f ) ¦ ¨1  ¸ t K (6) j 1 § Es · 2) Lowest Waiting Time First Out (LWTFO): RLC PDUs ¨ D j ˜ Rs, j ˜ ¨ ¸ ¸ ¨ © N0 ¹ ¸ are stamped with a maximum Waiting Time (WT) that © j ¹ depends on the QoS requirements of the service. RLC where Dj is the activity factor of source j and f is the ratio between inter and intracell interference. Cres is lower this delay, which is decreased each TTI the RLC packet limited by K (equal to 0.1 is considered in order to limit remains in the queue. In a TTI by TTI basis, the number the maximum interference level received in the BS, so of RLC packets in the queue and the remaining delay that thermal noise represents at least the 10% of determine an estimated transmission rate for each PDCP maximum total level). packet. When several LChs are multiplexed over the In the downlink, the total transmitted power of a same TrCh, the total estimated rate is the sum of the Radio Frequency (RF) carrier is shared by the users estimated rates of each service (7), and these rates are transmitting from the BS, so this limits the maximum given by the sum of each PDCP estimated rate according power allocated to one user, PMAX-BS,i, whereas in the to (8)-(10). uplink, there is a maximum tolerable interference level at Rest, j ¦¦( Rest,i, j,k  Rctrl, j,k ) (bps) (7) the BS receiver that is shared by the transmitting mobile kLCh i PDCP in TrCh j in queue k stations in the cell, each contributing to the interference ­ n _ rlci, j,k u SDU _ rlc(bits) which restricts the PMAX-UE,i value. ° ¦ , Wrem,i, j,k ! 0 °iPDCP Wrem,i, j,k (sec) As a function of traffic demands, TFC selection is °in queue k (8) Rest,i, j,k ® performed as long as output power constraints are met. If n _ rlci, j,k u SDU _ rlc(bits) ° , W 0 target TFC cannot be met, a TFC with lower rate and ° ¦ t (sec) rem,i, j,k °iPDCP TTI consequently lower power requirement is selected. The ¯in queue k TFC must be chosen among a set of TFCs (Transport Wrem,i, j,k Wrem,i, j1,k  tTTI if Wrem,i, j,k ! 0 (9) Format Combination Set (TFCS)), provided by the Radio PDU _ pdcpi,k W (10) Resource Management (RRM) entity [4]. The RRM is rem.i,0,k R necessary to achieve an efficient use of the available target,k resources. The acceptance or rejection of a new user where n_rlci,j,k is the number of remaining RLC packets connection depends on the interference (or load) it adds in the queue associated to PDCP packet i for service to existing connections. When a new connection is (LCh) k in TTI j, PDU_pdcpi,k the size of PDPC packet i, accepted, through the admission control algorithm, or including padding to match the number of RLC load traffic conditions change, TFCS is decided by RRM segments, Wrem,i,j,k the remaining time for RLC packets for this user. This TFCS determines the list of allowed associated to PDCP packet i in TTI j and Rctrl,,j,k the TFCs and, consequently, the maximum allowed bit rate transmission rate associated to RLC control packets for for this connection. Once a user is allocated the TFCS, it service k. should select the appropriate TFC in a TTI by TTI basis, Once Rest,j is calculated, the TFC selection for TTI j is in order to guarantee the different QoS of the done according to the following rule: multiplexed services with the minimum load to the - If Rest,j > Rtarget Ÿ increase transmission rate (select TF network. The selected TFC in a TTI determines the whose rate is nearest to Rest,j). transmission rate for each of the multiplexed TrChs. - If Rest,j< Rtarget Ÿ if there are data to transmit, keep This selection is made based on power allocation target rate. If there are not, reduce transmission rate. provided by RRC, trying to maximize the total This strategy is compared to the situation of only transmission rate that brings the individual transmission power constraints (MBR): 2) Maximum Bit Rate (MBR): information is transmitted rates and error probabilities (through Eb/No matching). However, this strategy does not consider other QoS at highest available speed. Transmission rate is only requirements such as delay constraints or instant traffic reduced if there are not enough packets in the buffer. demands (buffer occupation), which make feasible to 3. System Model tune more precisely the QoS of each multiplexed service. In this paper, it is proposed an alternative strategy for In this work, the joint transmission of voice, video, TFC selection which takes into account all these service- interactive game and signalling for both links has been dependent factors: buffer occupation, target bit rate and studied. To model voice traffic a classical two state ON- delay constraints in addition to power constraints. This OFF Markov model has been used, with means TON (0.4 strategy tries to smooth traffic, keeping a transmission sec.) and TOFF (0.6 sec.), respectively. A H.263 Video rate equal to target bit rate if possible, and only trace file with target bit rate of 32 kbps has been increasing it if buffer occupation is higher than expected considered. Both frame size and frame rate are variable. according to the following policy (rate is decremented if Mean frame size is 903 bytes and mean interarrival time there are not enough packets to match the target rate): is 226 ms. A gaming model based on [7] has been 1) Target Rate with Delay Constraints (TRDC): implemented. Similar to other models it defines a packet information about the arrival times is taken into account. call arrival process and within each packet call a When upper layer (PDCP) [6] packets arrive at the RLC datagram arrival process (lognormally distributed with layer, an expected delay is calculated assuming a mean and standard deviation 160 ms.) The packet call transmission rate of Rtarget kbps for that LCh. Each RLC duration and the reading time (the time between packet segment belonging to this PDCP packet is stamped with calls) are exponentially distributed with mean 5 sec. The reading time starts at the successful transmission of all is considered. Propagation model proposed in [9] is datagrams generated during the previous packet call to adopted for path loss. Log-normally distributed emulate a closed loop transmission mode. Datagram size shadowing with standard deviation of 8 dB is also is set to 576 bytes. The resulting mean data rate during included. A multi-path fading environment (Channel the active period is 28.75 kbps. model 3 in [10]) is considered. 11dB antenna gain and The system simulation model considers a service thermal noise power of –103 dBm are assumed [9]. The multiplexing example corresponding to four different MS and BS have a maximum output power of 24 and 43 services conveyed by five different TrChs for both links: dBm according to [10]. The 12.2 kbps AMR speech service split into three TrChs [8], the 3.4 kbps signalling bearer, a video service 4. Performance evaluation and an interactive game. In order to analyse the different 4.1- Simulation conditions. TFC selection strategies, the video and gaming services have been mapped onto a single TrCh using different In order to assess the performance of the multiplexing Transport Formats (128, 64, 32 and 16 kbps). In this scheme and the different proposed strategies, a system study, voice is considered as a priority service, so first it level simulator for the UTRA (UMTS Terrestrial Access is decided if, according to power constraints, voice could Radio) FDD system, programmed in C++ [11] has been be transmitted. Once voice is allocated, video and game developed. The system level simulator allows to evaluate traffic demands are taken into account. Main TrChs the performance of different RRM strategies, including parameters are included in Table 1. QoS constraints and several traffic sources, propagation conditions, mobility required Eb/No of these services in a fast fading vehicular models and results from a physical layer simulator [12], environment are also included. Fig. 2 shows the [13]. The UMTS protocol stack (PDCP, RLC and MAC) multiplexing scheme for the uplink. and the multiplexing of Logical and Transport Channels Table 1. Transport Format Parameters are implemented. Off line results from the physical level

QoS Requirements Eb/No simulator (bit error distribution according to Eb/No) are CRC Channel Coding TTI BER BLER UPLINK DOWNLINK included through a Hidden Markov chain. This physical Signalling TrCH0 1x148 16 bits 1/3 Convolutional 40 ms - 1.0E-02 4.05 4.20 level simulator considers different aspects concerning TrCH1 1x81 4.49 4.73 12 1/3 Convolutional 20 5.0E-04 - 1x39 5.33 5.57 the physical layer (channel estimation, synchronization, AMR Speech TrCH2 1x103 1/3 Convolutional 1.0E-03 - 3.36 3.60 0 20 power control, etc.) including channel coding and TrCH3 1x60 1/2 Convolutional 5.0E-03 - 3.31 3.23 interleaving for all TFCs. Video, game and voice TrCH4 8x340 1.95 3.15 4x340 2.25 3.20 transmission have been simulated according to the Data 16 1/3 Turbocoding 20 -1.0E-02 2x340 2.77 3.40 multiplexing scheme described in Section 3. Simulations 1x340 3.45 3.80 have been carried out with different load conditions. In

LOGICAL AMR Speech Real Time Video +Interactive Game Signalling the uplink, the mean number of video users in the same CHANNELS (12.2 kbps) ( 128 kbps) (3.4 kbps) cell ranges from 15 to 30. In the downlink, the transmission power for the test user is considered to be TRANSPORT CHANNELS TrBks 81 103 60 340 340 ... 340 148 limited to 5% of the maximum transmission power for 8 nTrBks the BS, whereas the load conditions are expressed in CRC attachment 93 103 60 356 356 ... 356 164

TrBk Concatenation 93 103 60 2848 164 terms of the fraction of available power that BS is Channel coding 303 333 136 8556 516 actually transmitting (% utilization, from 25 to 100). The Interframe interleaving 304 334 136 8556 516 considered QoS parameters [14] for voice and video Frame segmentation 152 152 167 167 68 68 4278 4278 129 129 129 129

Rate matching 359 359 352 352 202 202 8491 8491 196 196 196 196 transmission are a maximum delay of 400 ms and a packet loss of 3%. Game transmission requires a packet TrCh MULT IPL EXI NG 359 352 2028491 196 359 352 202 8491 196 ... delay lower than 250 ms without packet loss. Intraframe interleaving 9600 9600 ...

PHYSICAL Video and Game services are multiplexed over the CHANNEL DPDCH (960 kbps) Radio frame 4N Radio frame 4N+1 ... same TrCh using both FIFO and LWTFO dequeueing DPCCH (15 kbps) Radio frame 4N Radio frame 4N+1 ... Figure 2. Multiplexing scheme in the uplink. strategies. In the latter, the maximum waiting time (WT) stamped in RLC packets is based on the QoS Different RLC modes are selected for both services: requirements. For video packets, this time is considered TM mode is considered for AMR speech service, and equal to the discarding time. For game packets, the AM is selected for the video and gaming applications. maximum WT is set to 250 ms. TFC selection is Early discard will not be applied to the interactive game, implemented as described in Section 2 as it requires data integrity. This is carried out with video In addition, it has been studied the effect of an traffic since this is error tolerant. According to the estimation error in the transmitted power and the system chosen video traffic source, a variable value for Timer capacity in the uplink, leading to a deviation of the real Discard has been selected with Tmargin equal to 174 ms. Es/No from the target Es/No, in order to obtain results for The user is located in a hexagonal cell with radius 2 Km. a more realistic situation. The system load, unlinke Only the interference from the first-tier of adjacent cells propagation channel, suffers discrete changes in a TTI by TTI basis instead of a continuous evolution. Power TRDC. This figure shows that the LWTFO dequeueing control slowly adapts to these variations and several slots strategy provides a more balanced performance are needed to reach again the new target Es/No. To model achieving the requirements for both services. The mean this effect, the system capacity – Cres in (5) – is estimated transmission rate is similar for both MBR and TRDC, as a function of the capacity in previous and current TTI. unlike TF distribution (Fig. 7). TRDC smoothes traffic, Secondly, the target Es/No cannot be ideally estimated whereas in MBR, transmission rate mainly alternates and this has been modelled adding a lognormally between 0 and 128 kbps. From a network management distributed error to the estimated transmission power. perspective, although MBR obviously outperforms P P  lognorm(desv) (11) TRDC, this one would be preferred to avoid high rate T _UE est T _UE obj fluctuations that would lead to errors in load estimation. where PT_UE is evaluated according to (5), and the Cres in 2.50 TRDC -FIFO TRDC-LWTFO this equation is calculated as follows: MBR -FIFO MBR-LWTFO 2.00 curr prev Cres D 100 ˜ Cest  1  D 100 ˜ Cest (12) prev curr 1.50 The Cres and Cres values correspond to the previous and current TTI capacities respectively and is the 1.00 D (%) Discard percentage of the current capacity considered in the 0.50 estimation. 0.00 15 20 25 30 4.2- Results. Capacity (Number of users) Fig. 3 shows the percentage of packet loss for voice Figure 4. Dropped video packets (%) in the uplink 12.00 transmission. The QoS requirement is covered in all the TRDC -FIFO TRDC-LWTFO MBR -FIFO MBR-LWT FO simulated load conditions for both links. 10.00

8.00 1.40 DOWNLINK UPLINK 6.00 1.35

4.00 1.30 2.00

1.25 (%) ms > 250 Packet Delay 0.00

Packet Loss (%) Loss Packet 15 20 25 30 1.20 Capacity (Number of users)

1.15 (15, 25) (20, 75) (25, 75) (30, 100) Figure 5. Game packets with delay higher than 250 Capacity (Nusers,%utiliz) ms (%) in the uplink Video - packet loss - FIFO Video - packet loss - LWTFO Figure 3. Packet loss for voice transmission Game - delay - FIFO Game - delay - LWTFO 12.00 3.50 e 3.00 With the MBR strategy packets are transmitted faster 3.00 10.00 12.00 ) 2.50 10.002.50 than with TRDC, since the former uses the maximum 8.00 available resources (transmission rate) without trying to 2.00 8.002.00 6.00 1.50 6.00 keep a medium target bit rate. Therefore, dropping 1.50 1.00 4.00 4.00 1.00 probability for video packets is higher with TRDC, as it Loss Packet Video (%) packet delay ( >250 ms ) - % - ) ms >250 ( delay packet

0.50 % - ) ms >250 ( delay packet 2.00

2.00 (% ms 250 > Delay Packet Game FIFO Video packet loss - Game Game - loss Video packet FIFO is shown in Fig. 4. For both strategies, the LWTFO 0.50 Gam - loss packet Video LWTFO 0.00 0.00 25 50 75 100 dequeueing strategy provides a slightly worse 0.00 Capacity (% utilization) 0.00 25 50 75 100 performance for video packets. As game requirements Capacity (% utilization) are more restrictive, video packets are dealt with less Figure 6. Video packet loss and game packets with priority. In any case, with a 3% constraint for packet delay higher than 250 ms (%). (TRDC, downlink). loss, the requirements are covered. However, if the threshold were located at 1%, at certain load conditions, Fig. 8 and Fig. 9 show the effect of estimation errors time discard should be longer leading to an increase in for TRDC–LWTFO in the uplink. In Fig. 8, Cres is packet delay. Fig. 5 shows the percentage of game calculated according to (12) with D = 50%. Discarding packets with a delay higher than 250 ms. It shows that probability for video packets rapidly increases specially the LWTFO dequeueing strategy provides an important from a standard deviation of 0.5 dB, which would be the improvement. If we consider an acceptable threshold of maximum tolerable value for matching the QoS 3%, FIFO strategy does not work properly. LWTFO requirements for all load conditions. Fig. 9 shows the should be the appropriate strategy so that both QoS percentage of game packets with a delay higher than 250 requirements (video and game) were satisfied. Results ms. for different grades of accuracy in the capacity for the downlink are analogous. An example is shown in estimation for 15 users on average. The percentage of Fig. 6, which compares the performance of video and current capacity used in equation (12), models how game transmission under the same conditions using rapidly the power control adapts to the changes in the real system capacity. The faster is the adaptation, the higher is the contribution of the current value, which is maximum available bit rate (MBR). Multiplexing of expressed with a higher percentage. Sharp hops in LChs onto TrChs has been analysed by means of two capacity are due to heavily fluctuations in the system different dequeueing strategies. The performance of the load. In this situation, a realistic approximation is to proposed scheme has been evaluated through a realistic consider lower values of D, since it is more difficult to UMTS simulator under different load conditions and in a follow these variations. As it is shown in Fig. 9, this high mobility situation. The effect of a non-ideal power leads to a poor performance, even with a low power control has been included. Results show that a TFC error estimation. TRDC strategy for TFC selection tries selection according to traffic demands and delay to smooth traffic in order to yield a more stable load in constraints (TRDC strategy) matches the QoS the system reducing, consequently, the deviations in the requirements, with lower performance than MBR, but Es/No due to the difficulties of power control in with a more stable resource utilization. These lower load following the capacity variations, then leading to a better fluctuations allow to tolerate higher power estimation system performance. errors. For LCh multiplexing, a dequeueing strategy that 100% 128.00 takes into account QoS requirements (Waiting Time) provides a more balanced performance of the 80%

) 128 kbps 96.00 64 kpbs multiplexed services. 32 kbps 60% 16 kbps 64.00 Acknowledgment 0 kbps 40% Rmean This work was supported by projects from CICYT and

TF Distribution (% 32.00 20% FEDER, TIC2001-2481 and Telefónica Móviles de España. Transmission Rate(kbps)

0% 0.00 References UL DL UL DL TRDC MBR [1] 3GPP Technical Specification 25.321 v5.4.0 (2003-03) Medium Access Control (MAC) protocol specification. Figure 7. TF Distribution. Capacity (20, 50%) [2] 3GPP Technical Specification.25.212 v5.3.0 (2002-12) 5 Multiplexing and Channel Coding (FDD). 4.5 15 users 20 users [3] 3GPP Technical Specification 25.322 v5.4.0 (2003-03) 4 25 users 3.5 30 users Radio Link Control (RLC) protocol specification. 3 [4] 3GPP Technical Specification 25.922 v5.0.0 (2002-03) 2.5 Radio Resource Management strategies. 2 Discard (%) Discard [5] S. Baey, M.Dumas and M.C. Dumas, “QoS Tuning and 1.5

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0% [8] 3GPP Technical Specification 25.944 v4.1.0 (2001-06) 6 25% 50% Channel coding and multiplexing examples. 75% 5 100% [9] 3GPP Technical Specification 25.942 v6.0.0 (2002-12) 4 RF system scenarios.

3 [10] 3GPP Technical Specification 25.101 v5.5.0 (2002-12)

2 UE Radio transmission and reception (FDD). P(delay > 250 ms) (%) 250 ms) > P(delay

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