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A Method for Efficient Resource Allocation in UMTS TDD Mode in Multi-Service Context Disclosure Number: IPCOM000005360D
Original Publication Date: 2001-Aug-31
Included in the Prior Art Database: 2001-Aug-31
Document File: 5 page(s) / 35K

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A Method for Efficient Resource Allocation in UMTS TDD Mode in Multi-Service Context

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A Method for Efficient Resource Allocation in UMTS TDD Mode in Multi-Service Context

by Doru CALIN, Marc ARENY, Arnauld TAFFIN

No detailed algorithms currently exist to handle multi-service supply in TDD mode. Basically, access to resources (codes time slots) is allocated by evaluating the level of interference on the existing time slots. This is not enough to support services having different requirements in terms of delay and Bit Error

Rate (BER) or Signal to Interference Ratio (SIR).

The main problem still unsolved is that the overall performance would be inherently strongly affected by mixing services with high disparities in their requirements (BER, power control needs, delay constraints, packet loss tolerance) without an adequate packet scheduling protocol whose objective is to consider properly individual services needs.

The major disadvantages of resources allocation techniques based only on the measured levels of interference [1] are :

Mutual interference: since codes are not 100% orthogonal, simultaneous communications with opposite requirements carried out on the same slot will interfere with each other even when joint detection is implemented.

Since the interference is unlikely to be uniformly distributed in hot spot traffic areas and in the presence of high bit data rate traffic (usually bursty), the same link might simultaneously experience varying qualities during the same frame.

The maximum capacity of each slot will be restricted by the service having the most stringent need, which in turn will decrease the spectrum efficiency. Especially, if low bit rate and high bit rate applications are mixed together on the same slot, low bit data rate services will be affected by this co-existence (e.g. power control becomes less efficient due to the presence of active high data rate connection(s)).

Proposed Solution to the Problem(s)

The underlying idea is that reducing the number of calls on the same slot at minimum will diminish the mutual interference, while the slot utilisation will be maximised. In our solutions, multi-rate operation is done by allocating (most) codes belonging to the same connection on the same slot whenever it is possible to simplify the power control operation. This way all drawbacks presented above are eliminated. To make this possible and in order to maximise the throughput, some slots will be reserved for high-bit data rate traffic which is sensible to delay. Other traffic flows having lower priorities could, however, use these slots as long as enough available capacity exists. However, upon arrival of a high bit data rate call (burst) the lower priority traffic will be scheduled on another slot (re-arrangement) or dropped (or forced to wait) till some resources become again free for access.

Algorithm for radio resource allocation;

Let's consider N classes which compete together for the same resources. These classes are noted by {1, 2, 3, 4, ..., i, i+1, ..., N}. With this generalisation one notices:

The number of slots requi...