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ENHANCED STRATEGY FOR TIME SLOT SELECTION IN A TD-CDMA SYSTEM

IP.com Disclosure Number: IPCOM000011628D
Original Publication Date: 2003-Mar-10
Included in the Prior Art Database: 2003-Mar-10
Document File: 5 page(s) / 97K

Publishing Venue

Motorola

Related People

N. Motte: AUTHOR [+3]

Abstract

Purpose of this paper is to propose a new strategy for the Time Slot selection in a TD-CDMA system. Indeed, in case of mixed services (like Speech and Web), the Call Admission control does not take into account that these both services could be incompatible in the radio point of view, incompatible meaning that the impact of one service on the another one is not negligible resulting for instance in an increase of the Frame Error Rate for the most sensitive service. In order to select the same Time Slot for two incompatible services, this paper proposes a new Time Slot selection in a TD-CDMA system based on the following parameters: interference level, number of available codes and compatibility between services.

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ENHANCED STRATEGY FOR TIME SLOT SELECTION

IN A TD-CDMA SYSTEM

by N. Motte, D. Grandblaise, R. Pintenet

Abstract

Purpose of this paper is to propose a new strategy for the Time Slot selection in a TD-CDMA system. Indeed, in case of mixed services (like Speech and Web), the Call Admission control does not take into account that these both services could be incompatible in the radio point of view, incompatible meaning that the impact of one service on the another one is not negligible resulting for instance in an increase of the Frame Error Rate for the most sensitive service. In order to select the same Time Slot for two incompatible services, this paper proposes a new Time Slot selection in a TD-CDMA system based on the following parameters: interference level, number of available codes and compatibility between services.

Problem(s) To Be Solved

Different strategies are adopted for the Call Admission Control (CAC) in a TD-CDMA system. Since TD-CDMA is interference limited, the best solution for the selection of the Time Slot (TS) was to consider the interference level in each TS of the TDD Frame and to select the less interfered one.

For speech service, the CAC is based on this interference level. The Time Slot (TS) having the minimum interference level is selected. Then, the availability of codes is checked and if enough codes are available, the computation of the initial power is performed. If this initial power is not higher than the maximum allowed one, the communication starts. For Web, it is different. Since Web user requires a higher Bitrate, they also require the use of more than one code in the TDD frame. In order to be as efficient as possible, the CAC is not the same and is based on the availability of codes per TS. The TS having the higher number of available codes has the highest priority. The initial power is then computed and if not too big, the communication starts.

In case of mixed services (Speech, Web), the CAC are the same as described previously. The compatibility between services is not taken into account. If two services are incompatible (i.e. impact of one service on the another one is not negligible), it is possible to select the same TS for one speech user and one web user; the problem being that the burstiness of Web service degrades a lot the call quality of speech user. It results in an increase of the Frame Error Rate for each user, i.e. increasing the percentage of Bad Quality Call users.

Proposed Solution to the Problem(s)

This paper proposes a new scheme for the selection of the Time Slot in a TD-CDMA system taking into account all following parameters: interference level, number of available codes and compatibility between services. In order to do this, each parameter is associated to a probability function. These three probability functions are then used to compute the final probability. The TS having the highest final probability is selected to carry the considered service.

 

Interference Level Probability Fun...