Sverker Magnusson

Performance of link admission control in a WCDMA system with HS-DSCH and mixed services

Link admission control is one of the fundamental radio resource management functions in radio networks, determining which users should have access to the radio channels. The introduction of the shared high-speed channel, HS-DSCH, in release 5 of WCDMA poses new requirements on such an algorithm. Different kinds of users on dedicated as well as the shared high-speed channel must be handled so that radio resources are allocated properly among different kinds of services, and so that overload situations are avoided. A simple threshold algorithm is evaluated here in a mixed services scenario where speech users are allocated to dedicated channels and data users to the HS-DSCH. The threshold applies to the total power used by the non-HS channels in each cell. By selecting the threshold appropriately, resources can be shared efficiently between the two types of services while avoiding overload situations.

Bluetooth radio network performance: measurement results and simulation models

When designing new communication systems, results from simulations determine a large part of the system parameters. As simulations simplify reality according to the investigated aspects, the results obtained strongly depend on the assumptions made for the simplifications. This paper now presents real-life measurement results obtained in a Bluetooth radio network testbed and compares these results with models used in radio network simulations. Three scenarios have been considered: the noise limited scenario, Bluetooth interfered by microwave ovens and Bluetooth interfered by IEEE 802.11b. It is shown that when including free space propagation, Rayleigh fading and the antenna orientation (with 3 dB between aligned and orthogonal) a good simulative approximation of the noise limited behaviour is possible. In case of interference the distance to the interferer as well as its time-frequency behaviour has to be considered: For IEEE 802.11b a 17 MHz bandwidth and an activity according to its relative throughput should be modelled, for the microwave oven a time limited activity over 61 carriers with a frequency dependent interference power.

Collision properties of GSM hopping sequences

Properties of GSM pseudo-random frequency hopping sequences (FHSs) are investigated and it is concluded that they differ significantly from the properties of ideal random sequences. Such discrepancies are evident from correlations as well as collision rates between sequences. It is shown that the collision rate between two FHSs depends heavily on certain FHS parameters such as the hopping sequence number (HSN) and the mobile allocation index offset (MAIO). Another important parameter with significant impact on the collision rate is the frame number (FN) difference between two cells. A consequence is that co-channel interference between cells with fractional loading can be reduced by careful HSN/FN/MAIO planning based solely on collision rate information. This is demonstrated in examples involving two cells.