Jeroen Wigard

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

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.

On the User Performance of LTE UE Power Savings Schemes with Discontinuous Reception in LTE

The UTRAN long-term evolution (LTE) specifications provide flexible means to achieve micro-sleep operation for user equipment (UE) even though it is in active mode and running a service. By means of a discontinuous reception (DRX) framework, pauses in the transmission due to natural traffic characteristics or network prioritization can be utilized. The specifications give a number of options to optimize the performance. In this paper two of those possibilities are compared. Long DRX with the use of an inactivity timer is compared to the usage of short DRX on top of long DRX. The performance is evaluated in terms of user throughput, power consumption, and network performance, while using a realistic RF modem power consumption model for the UE. For bursty traffic, short DRX shows a gain of up to 100% over DRX with just an inactivity timer, when measuring throughput per power unit consumed in case of one or multiple users being present in the cell.

Balancing power saving and single user experience with discontinuous reception in LTE

The UTRAN long-term evolution (LTE) provides flexible means to achieve micro-sleep operation for user equipment (UE) even though it is in active mode and running a service. By means of a discontinuous reception (DRX) framework pauses in transmission due to natural traffic characteristics or network prioritization can be utilized. However, the optimum setting of parameters must be provided as a compromise among reaction latency, user throughput, power consumption, and network performance. Using a realistic RF modem power consumption model for the UE, we investigate different algorithms for optimizing the balance among user throughput and power saving using a Web-browsing session as the reference. We show that with proper configuration of the DRX parameters we can optimally achieve a 95% reduction of the UE power consumption with only a moderate and acceptable 10-20% loss of experienced throughput.

Interference Based Power Control Performance in LTE Uplink

In LTE uplink, the slow varying path gain and shadowing are compensated by the standardized open loop power control (OLPC). Further optimization of the system performance can be done via closed loop power control commands. In this contribution, it is shown that using such commands to control the interference caused by users to the system, it is possible to achieve a gain in the order of 20% on the average cell throughput while maintaining the same outage cell throughput compared to the performance of the OLPC. Furthermore, gain on both average and outage cell throughput can be achieved by tuning the parameters of the proposed scheme.

On the Performance of Integrator Handover Algorithm in LTE Networks

The 3GPP UTRAN Long Term Evolution (LTE) system utilizes packet based architecture with distributed mobility management, where the E-UTRANNode-B (eNB) takes the responsibility of making the hard handover/handoff (HO) decisions based on the user equipment (UE) measurements. To cope with the corner effect due to the loss of the line of sight (LOS), a fast HO decision algorithm is required which can guarantee the LTE seamless HO requirement and keep the quality of service (QoS) criteria. In this paper, a HO decision algorithm, the integrator algorithm, has been evaluated in the Manhattan scenario, and is compared with the traditional power budget (PBGT) handover. The study focuses on the LTE intra-frequency HO scenario and uses the reference symbol received power (RSRP) measurement as input. The results show that the integrator algorithm has the same performance as the PBGT algorithm based on the number of HOs per UE and signal to interference plus noise ratio (SINR) evaluations for different UE speeds.

Load adaptive power control in LTE Uplink

In LTE Uplink, the slow varying pathgain and shadowing are compensated by the standardized open loop power control (OLPC) which is based on a power density offset and a compensating factor for the pathloss experienced by the users. The optimization of those parameters reveals a dependency on the allocated bandwidth. A Load Adaptive Power Control (LAPC) algorithm is proposed to handle the bandwidth variations and ensure optimal system performance. In this contribution it is shown that using closed loop power control commands to adapt the transmission power density to the used bandwidth, it is possible to achieve coverage gains up to 60% while maintaining a cell throughput comparable to the reference case.

Capacity of a GSM network with fractional loading and random frequency hopping

The need for more capacity in GSM networks is increasing. Using random frequency hopping and fractional loading is a potential way to obtain more capacity. In this paper the optimal reuse scheme for a GSM system with random frequency hopping is presented along with some methods to increase the capacity and to improve the link quality, like using DTX and fractional loading. The 1/3 reuse scheme appears to be best if the capacity is determined by looking at the distribution of signal to interference (CIR) values, while the 3/9 reuse scheme seems best if the focus is at the percentage of dropped calls (with the used dropped call, power control and handover algorithm). The 1/3 reuse scheme has the advantage over the 3/9 reuse scheme that it is able to profit from fractional loading, which gives better quality to the individual user.

On the Impact of Realistic Control Channel Constraints on QoS Provisioning in UTRAN LTE

This paper focuses on the Physical Downlink Control Channel (PDCCH) and describes the impact of its realistic constraints. Specifically, the impact on the performance of the UTRAN LTE FDD downlink and on the QoS provisioning is studied. It is described, when adopting a QoS-aware packet scheduling policy, how scheduling limitations due to control channel may affect the scheduler behavior. It is shown that the system level performance degradation could be kept negligible utilizing the dynamic link-adaptation mechanisms available on the control channel and adopting careful control channel- related design solutions. Therefore, assuming a proper dimensioning in terms of OFDM symbols reserved for control, the PDCCH could simply be modeled for LTE FDD system level simulation purposes by limiting the number of PDCCH allocations. Such a number primarily depends on the system bandwidth.

A simple mapping from C/I to FER and BER for a GSM type of air-interface

To evaluate the performance of a mobile radio system, both network and link quality aspects have to be evaluated. A network simulator is often used to find the influence of different system parameters, such as DTX, frequency hopping and power control. To complete the evaluation, a link simulator has to be integrated in the network simulator, so that each radio link can be simulated. An obvious method to integrate the radio link quality aspects with the network simulator is to use the output of the network part of the simulator as input for an integrated link simulator. This will however lead to time consuming simulations, In this paper a simpler method is presented, which leads to a shorter simulation time. The output of the network part of the simulator, expressed in signal to interference (C/I) values, is used as input for look-up tables, which lead to a BER and a frame erasure rate (FER) for each radio link. These look-up tables are depending on the hopping pattern and channel profile and they are also receiver dependent. The results of the mapping method are good, except for a few situations, where the prediction of the BER goes wrong. This happens when sequential hopping with a few frequencies is used and the speed of the mobile user is low. In general the presented predictions are within 1 dB (FER) and within 0.2 dB (BER).

Power Savings and QoS Impact for VoIP Application with DRX/DTX Feature in LTE

In the Long Term Evolution system Discontinuous Transmission and Reception (DRX/DTX) has been introduced to extend the terminal battery lifetime. In this paper, we study the energy-saving provided by this mechanism and the impact on the QoS performance of Voice over IP (VoIP) traffic under dynamic and semi persistent packet scheduling strategies. Simulations and analytical results show that the DRX/DTX scheme can reduce the terminal power consumption without compromising the required VoIP QoS in terms of maximum air-interface delay. However, it does not provide any further power savings if the terminal is asleep for a period longer than 20 ms. It is shown that the power savings are larger for semi persistent scheduling than for dynamic packet scheduling at the cost of a lower spectral efficiency.