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Position based adaptation of modulation techniques and its efficient representation

IP.com Disclosure Number: IPCOM000031857D
Original Publication Date: 2004-Oct-14
Included in the Prior Art Database: 2004-Oct-14
Document File: 3 page(s) / 51K

Publishing Venue

Motorola

Related People

Dipendra Chowdhary: AUTHOR [+2]

Abstract

A wireless digital communication system uses adaptive modulation to improve channel utilization or to provide higher data rates. It also uses adaptive power control to improve the battery life. In both the cases, adaptation (at the mobile radio) is dependent upon the feedback from the Base Site. The feedback requires measurement by the Base Site. This causes certain delays in adaptation resulting in inefficient use of resources during adaptation process.

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Position based adaptation of modulation techniques and its efficient representation

By Dipendra Chowdhary, Rob Biggs

Problem

A wireless digital communication system uses adaptive modulation to improve channel utilization or to provide higher data rates. It also uses adaptive power control to improve the battery life. In both the cases, adaptation (at the mobile radio) is dependent upon the feedback from the Base Site. The feedback requires measurement by the Base Site. This causes certain delays in adaptation resulting in inefficient use of resources during adaptation process.

Solution

This paper provides a way to solve the initial delay due to adaptation process. The paper proposes that the selection of initial modulation technique or initial power should be a function of position of the mobile transmitter. It is assumed here that the receiver has a fixed location.


The details are as follows:
1. The transmitting mobile radio has a map for every site. The map has an estimate of the optimal modulation technique and power for every position.
2. The transmitting mobile radio gets its position and velocity using GPS.
3. The mobile radio uses its position to look into the map and gets the recommended modulation technique and power for that location. It further uses the velocity to refine the modulation technique and power.
4. The transmitting radio uses the modulation technique (obtained from step 3) as the initial modulation technique for the adaptive modulation process.
5. There is some probability that the modulation technique may fail. Optionally, the radio can use the failure information to learn and modify the map.
6. The map can be modified by sending the changed map data over the air to an application on the mobile radio.

The optimal modulation technique is dependent upon many factors such as distance from the Base Site, attenuation caused by buildings or other obstacles, velocity of the mobile, external interference, and environmental conditions. The position based adaptation takes care of the first three factors.

An efficient representation

The above technique for adaptation of operational parameters requires a mobile radio to store a map (position vs. parameter) for each geographical region in which the radio operates. A mobile radio has a restricted amount of memory and processing power and therefore the representation should be efficient in using the resources of the mobile radio. This section describes an efficient method to represent the type of map required for a mobile radio.

Traditional region representations can be used to code the boundary of regions. This representation is very local in application. It is neither efficient in memory utilization nor in searching for a position.
Hierarchical region representation uses "quad tree", which is based on the successive subdivision of the region into four equal sized blocks until a block is entirely of one type. The quad tree is more global in nature and enables the elimination of larg...