1. IEEE 802.21 MEDIA INDEPENDENT HANDOVER DCN: 21-08-0004-00-mrpm
Title: Power Management in Out-of-Coverage Areas for Multi-Radios
Date Submitted: Jan. 03, 2008
Presented at IEEE session #24, in Taipei, Taiwan
Authors or Source(s): James Han (Motorola)
Abstract: Power management in out-of-coverage areas is a challenge to single-radio mobile stations in cellular networks. The same approach is not applicable to multiple-radios mobile stations. Use cases for multiple-radios power management in out-of-coverage areas are provided and a possible solution based on information service is described.
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2. IEEE 802.21 presentation release statements
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The contributor is familiar with IEEE patent policy, as outlined in Section 6.3 of the IEEE-SA Standards Board Operations Manual < and in Understanding Patent Issues During IEEE Standards Development
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3. Use Cases of Multi-Radio Power Management in Out-of-Coverage Areas
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4. Problem Statement
Power management of a single radio in out-of-coverage areas is a challenge to cellular mobile stations. There is a trade-off between the frequent scan-and-camp and the prompt service establishment when the radio comes back to the coverage areas. That is,
If the mobile station frequently scans and camps, then it consumes more power in the out-of-coverage areas; by doing so, the mobile station will promptly establish its service as soon as it re-enters the coverage areas.
However, if the mobile station less frequently scans and camps, then it will consumes less power in the out-of-coverage areas; but its service establishment will be delayed when it re-enters the coverage areas
If we use the same power management approach as in out-of-coverage areas for the single radio of cellular mobile stations, then the power drain of the multiple-radios mobile station will increase dramatically as the number of radios increases. This approach is unacceptable for end-users.
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5. Scenarios in Out-of-Coverage Areas
Use case assumption:
The mobile station has WiFi and WiMAX radios.
Let’s look at the following scenarios,
Scenario 1: the area has WiFi, but no WiMAX coverage
Scenario 2: the area has WiMAX, but no WiFi coverage
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6. Possible Solution (I) For Scenario 1,
WiFi connection is active with data services and the WiMAX radio is off or in deep sleep mode in the area;
When the mobile station moves, its location is updated in the WiFi network (as the use case discussed before in MRPM);
Based on its location in WiFi network, the mobile station can see whether there is a coverage of WiMAX through querying MIH information service on WiMAX coverage map and its current location;
If there is no WiMAX coverage, the WiMAX radio continues to stay in its off or deep sleep mode;
Otherwise, the WiMAX radio will wake up and start to scan and camp
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7. Possible Solution (II)
This solution makes the mobile station not blindly scan and camp to drain power when there is no WiMAX coverage. It dramatically reduced the power drains of WiMAX radio in the out-of-coverage areas of WiMAX.
By promptly MS location updating in WiFi network and querying the MIH information service through established WiFi connection, the WiMAX coverage can be promptly detected.
The latency of service establishment when the MS re-enters the WiMAX coverage areas can be set as a design parameters for out-of-coverage areas of WiMAX of the multi-radio MS.
Similar solution is applicable to Scenario 2.
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