A lightweight method of maximizing radio?s transmitting coverage in direct communication mode
Original Publication Date: 2014-Oct-17
Included in the Prior Art Database: 2014-Oct-17
Zhao, Dong: INVENTOR [+3]
Please refer to the attached slides.
By Zhao Dong-A20174, Liang Shiqiang-NKJG84, Yu Changlin-NXR836
Motorola Solutions, Inc.
This idea provides a solution based on the number of neighbors in subscriber’s (SU’s) direct communication range to extent the coverage of package or message in direct communication mode. With this idea, initiating SU is able to transmit the package with maximized coverage.
In direct communication mode, the communication coverage of each subscriber (SU) is limited due to the relatively low transmitting power and restricted to some geographic area. It’s an unexpected problem that the packets sent from one SU is not able to reach other SUs who are out of the initiating SU’s direct communication range.
As shown in Figure 1, SU2, SU4, SU5 and SU6 are out of communication range of SU0. If an emergency message sent by SU0, this message could be only received by SU1 and SU3. Most other SUs out range of SU0 in this group are still uninformed with SU0’s emergency condition.
This solution is able to automatically select the best relay SU to relay the message to as many of the SUs as possible for the extended coverage in a timely manner. It consists of a format description about relay request packet, an algorithm regarding how to relay the request packet, and a method of discarding identical received packet.
There is a pre-condition for this solution that all SUs in direct communication mode generate and dynamically maintain PDT (Partner Device Table) which contains the list of the neighbor SUs in its direct communication range.
RRS (Relay Request SU) sends packet with the relay flag and the initial packet sequence# set. Other SUs, who received the relay request packet, will resend this packet out according to the number of its neighbors in its PDT, or discard it if this is a previously received identical packet. By repeating the above steps in multihop, the relay packet will be propagated with the extended coverage.
This section describes the key details of this solution about how to send relay request packet, re-transmit received packet or discard it while received.
o RRS (Relay Request SU) sends packet with the relay flag set.
o SUs in the direct communication range detect this packet, and relay it after delaying for a time interval inversely proportional to the number of SU in PDT, but proportional to its battery level. So the SU, who has the most number neighbors and with best battery level, will re-transmit this packet out firstly.
o Upon the receipt of the relayed packet (it contains the ID of initial RRS, and packet sequence#), the other SUs, which have a pending packet from RRS of the same ID and identical packet sequence#, discard the pending relay packet; while for RRS, it will consider it as the acknowledgement for the sent packet by itself.
o Any SU receives the duplicated relayed...