Showing papers by "Preben Mogensen published in 2004"

System Level Performance of the M-LWDF Scheduling Algorithm for Streaming Services in HSDPA

Abstract: The present paper analyzes the paradigm of providing streaming services over HSDPA. The provision of QoS to streaming users imposes two major challenges on the HSDPA technology, namely, satisfying the guaranteed bit rate and delay jitter constraints. Focusing on the latter QoS requirement, the operation of the packet scheduling functionality completely determines the node B queuing streaming packets prior to their transmission through the radio interface, and therefore the scheduler plays a key role in the satisfaction of the delay jitter constraint.

Performance of the M-LWDF scheduling algorithm for streaming services in HSDPA

Abstract: The present paper analyzes the paradigm of providing streaming services over HSDPA. The provision of QoS to streaming users imposes two major challenges on the HSDPA technology, namely, satisfying the guaranteed bit rate and delay jitter constraints. Focusing on the latter QoS requirement, the operation of the packet scheduling functionality completely determines the node B queuing streaming packets prior to their transmission through the radio interface, and therefore the scheduler plays a key role in the satisfaction of the delay jitter constraint.

Network performance of mixed traffic on high speed downlink packet access and dedicated channels in WCDMA [cellular radio]

Abstract: Downlink throughput results are presented for cases where the available cell transmission resources are shared between high speed downlink packet access (HSDPA) and dedicated channel users. It is shown that the total cell throughput can be increased by 69% by allocating only 5 high speed downlink shared channel codes and 7 W for HSDPA transmission, compared to a scenario without HSDPA enabled. These results are obtained for a macro cellular scenario with best effort packet traffic. It is demonstrated that part of this throughput increase originates from a better utilization of available cell transmit power when HSDPA is introduced, since reservation of less power control headroom is required.

Performance of packet scheduling methods with different degree of fairness in HSDPA

Abstract: The present paper focuses on assessing the performance of the packet scheduler in HSDPA. The investigation has especially concentrated on assessing different scheduling methods with different degrees of fairness for non-delay-sensitive elastic traffic. The fairness ultimately determines the QoS perceived by the users. The results show that very unfair scheduling methods provide the highest HSDPA cell throughput for best effort NRT traffic, although, under heavy load situations, the unfairness of these policies causes the starvation of users under poor average radio propagation conditions. Under minimum user throughput guarantees, the proportional fair algorithm provides the highest cell capacity of all tested algorithms. With this scheduler, the provision of user throughput guarantees of CA, 128 and 384 kbit/s (for at least 95% of the users) incurs on a cell throughput reduction respectively of around 10, 30 and 80% relative to the maximum cell throughput for best effort traffic (i.e. no user throughput guarantees at all).

Mobility management and capacity analysis for high speed downlink packet access in WCDMA

Abstract: In this paper we discuss two options for supporting mobility management for HSDPA-users. Especially issues related to direct change of the serving HS-DSCH cell are addressed. where a handover from a HS-DSCH in the source cell to a HS-DSCH in the target cell is made. It is concluded that change of the serving HS-DSCH cell without any intermediate channel switching to DCH seems to be a promising solution from a performance point of view as it allows us to have full HSDPA cell coverage and high capacity gain from introducing HSDPA. Uplink HS-DPCCH coverage is also addressed for users with their DCH in soft handover mode.

Combined time and code division scheduling for enhanced uplink packet access in WCDMA

Abstract: This paper contains an evaluation of three different time and code division schedulers, for data transmission on enhanced dedicated channel (E-DCH) in WCDMA uplink. Time scheduling on E-DCH is possible thanks to fast node B scheduling operation on a transmission time interval (TTI) basis. Time scheduling allows for allocating users for transmission with instantaneously high data rates, and possibly when they experience favourable channel conditions. The system capacity can therefore be increased, also because interference generated to other cells is reduced. We apply a combined time and code division scheduling strategy in three different cases: a "blind fair throughput" scheduler (BFT), a "maximise transmit power efficiency" scheduler (MTPE) and a "channel-state aware fair throughput" scheduler (CSAFT). The two latter schedulers utilise an appositely defined uplink channel quality indicator (UCQI) to exploit channel-state information in the packet scheduling procedure. While the MTPE scheduler maximises cell throughput at the cost of at low degree of fairness between users, the CSAFT algorithm is shown to offer an appealing trade-off between users' fairness and throughput maximisation. Under a specific outage constraint for the packet call throughput, the capacity gain of the CSAFT scheduler over a node B code division scheduler is 17% and 30% for vehicular A and pedestrian A channel profile at 3 km/h, respectively. The estimated capacity increase compared to a reference RNC-based scheduler is estimated between 50% and 80%, also depending on the propagation scenario.

Capacity gain of beamforming techniques in a WCDMA system under channelization code constraints

Abstract: This study addresses the performance of a wideband code-division multiple-access mobile communications system with beamforming antenna arrays (AAs) at the base station, synthesizing a grid of beams. In order to fully exploit the capacity gain from beamforming without jeopardizing the stability of the system, a directional power-based admission control (AC) scheme is applied. Due to the higher capacity offered by beamforming techniques, shortage of orthogonal channelization codes in the downlink becomes an increasingly important factor, which may result in blocking of users before the interference power limit is reached. The problem of channelization code shortage is addressed, and a solution based on splitting the cell into several code regions is proposed. For a network with circuit switched data services operated at 64 kb/s, the capacity gain for an eight-element AA is found to equal a factor of 2.5 for a universal mobile telecommunications equivalent system, with one channelization code set per cell. The capacity gain is limited by severe channelization code shortage under these circumstances. This problem is solved by deploying a cell splitting strategy with multiple code regions, which subsequently results in a capacity gain increase to a factor of 3.4. Furthermore, the soft capacity mechanism associated with partial deployment of AAs in a subset of the cells in the network is also addressed. It is demonstrated that a hot spot cell with AAs also helps increase the capacity of the surrounding cells with conventional sector antennas when using a power-based AC strategy.

Performance of fast Node B scheduling and L1 HARQ schemes in WCDMA uplink packet access

Abstract: The performance of WCDMA uplink systems deploying Node B based scheduling and fast hybrid ARQ (HARQ) retransmission protocols is studied With fast Node B scheduling and fast L1 HARQ schemes, both the uplink packet scheduling functionality and the entity controlling the retransmission mechanism are moved from the radio network controller (RNC) to the Node B A Node B scheduling algorithm is proposed to increase the utilisation of the allocated uplink resources; this is achieved by making use of already existing information about the transmitted data rate of the UEs Moreover, fast L1 HARQ schemes make retransmissions less costly from a delay perspective compared to an equivalent RNC controlled ARQ mechanism Therefore, the physical channel can be operated with somewhat higher error probability, which converts directly into enhanced system capacity The potential capacity gain from fast L1 Node B controlled HARQ strategies and fast Node B scheduling operation is estimated by means of an analytical study, as well as system level simulations The combined gain obtained by jointly deploying fast Node B scheduling and fast L1 HARQ retransmission schemes is estimated in the range from 25% to 60%, depending on the mobility scenario Fast Node B scheduling and L1-based HARQ protocols are included in 3GPP's "Feasibility Study for Enhanced Uplink for UTRA FDD" (TR 25896 V112, 2003)

Capacity gain of an uplink-synchronous WCDMA system under channelization code constraints

Abstract: The performance of an uplink-synchronous wide-band code-division multiple-access (WCDMA) system is evaluated for radio environments with low temporal dispersion. The capacity gain of synchronous WCDMA is evaluated theoretically under certain constraints and by means of extensive dynamic system level simulations for more advanced scenarios. The effect of channelization code shortage, the impact of the dispersive radio channel on the orthogonality of received signals, and soft handover are some of the considered effects. The potential capacity gain is found to equal 35.8% in a multicell scenario, conditioned on an infinite number of channelization codes per cell. For a more realistic scenario with channelization code constraints, the capacity gain is reduced to 9.6%. The absolute number of users per cell, relative to the available number of channelization codes within each scrambling code group, is therefore found to be an important metric. This further suggests that the capacity gain of synchronous WCDMA decreases when other capacity-enhancing techniques are deployed, such as uplink antenna diversity, soft handover, voice activity detection, etc. The presented simulation results in the case where soft handover is not considered accurately match the analytical findings.

Effects of Other-Sector Interference Variation on Detection, Link Adaptation and Scheduling in HSDPA

Abstract: This paper analyses other-sector interference variation effects in the context of 3G WCDMA/HSDPA. It focuses particularly on the on/off power switching effect caused by partial HSDPA inactivity and on fast transmit antenna weight adaptation which occurs when closed loop transmit diversity is used. It is found that partial HSDPA inactivity and/or closed loop transmit diversity operation can cause symbol level SINR variation in the order of 2-4 dB. In the considered system with 56 interfering sectors, this leads to cell throughput losses up to 10% with proportional fair scheduling and perfect channel state feedback. Including channel quality indication inaccuracies, however, effects due to other-sector interference variation become negligible.

Geometry Based Other-Sector Interference Modelling for Downlink System Simulations

Abstract: An other-sector interference model is developed for the downlink of 3G cellular systems. It is solely based on the cell geometry factor and a user’s line of sight angle of connection to a serving base station antenna array. The dependency on just two parameters makes it especially suitable to support a decoupled approach of link and system level simulations, where the link simulations already account for other-sector interference effects. A comparison of the model with a standard 57 sector macrocellular set-up shows that for a 3-sector site deployment, modelling 5 out of 57 sectors with multipath fading characteristics delivers a good trade-off between simulation complexity and other-sector interference modelling accuracy. Keywords— Other-cell interference, other-sector interference, G-factor, quasi-static downlink system simulations.

Method and a controller for controlling a connection

Abstract: A method of controlling a connection comprising a first link and a second link is disclosed. The method comprises determining if one of the links is limiting capacity the connection and if so, changing one or more parameters relating to one of the links to change the capacity of the one of the links.

Method and apparatus for controlling a communication connection

Abstract: This invention relates to a method of controlling a connection comprising a first link and a second link, said method comprising the steps of determining if one of said links is limiting capacity of said connection and if so, changing one or more parameters relating to at least one of said links to change the capacity of at least one of said links.