Packet structure

A communication system comprising:

• a source node configured to transmit data in a multihop network, wherein the data includes a packet including a RACH area;
• and wherein the packet includes a hop number corresponding to a current number of times that the packet has been transmitted before reaching a destination node;
• and
• at least one relay node that is configured to receive the data and increment the hop number in the packet before transmitting the data on a path towards the destination node,
• wherein the at least one relay node is further configured to listen to packet transmissions at a previous hop and estimate a number of relay nodes in the previous hop by:
• synchronizing with an ongoing subsequent hop transmission of a packet;
• extracting values pertaining to a group of subcarriers v1-vNc listed in a RACH area of the packet;
• and
• detecting those subcarriers in the group of subcarriers v1-vNc whose energy content crosses a preset threshold, wherein the estimate of the number of relay nodes K in the previous hop correspond to a number of the subcarriers in the group that crossed the preset threshold,
• wherein the at least one relay node is further configured to optimize a value of a transmit power level based on the estimate of the number of relay nodes K in the previous hop and the hop number.

A method for operating a multihop network, comprising:

• formatting, by a source node, a packet that includes a dedicated field containing a hop number corresponding to a current number of times that the packet has been transmitted before reaching a destination node, wherein the packet further includes a RACH area;
• transmitting, by the source node, the packet including the RACH area and the hop number;
• receiving, by a relay node, the packet;
• incrementing, by the relay node, the hop number contained in the packet;
• transmitting, by the relay node, the packet on a path towards the destination node;
• listening, by the relay node, to packet transmissions at a previous hop and estimating a number of relay nodes in the previous hop by:
• extracting values pertaining to a group of subcarriers v1-vNc listed in a RACH area of the packet;
• and
• detecting those subcarriers in the group of subcarriers v1-vNc whose energy content crosses a preset threshold, wherein the estimate of the number of relay nodes K in the previous hop correspond to a number of the subcarriers in the group that crossed the preset threshold;
• and
• optimizing, by the relay node, a value of a transmit power level based on the estimate of the number of relay nodes K in the previous hop and the hop number.

A source node in a multihop network, comprising:

• a first circuit of the source node that is configured to listen to a RACH area during a packet transmission at a second hop and estimate a number of relay nodes in the second hop by detecting those subcarriers listed in the RACH area whose energy content crosses a preset threshold;
• a second circuit of the source node that is configured to receive a number of relay nodes at a destination stage transmitted by a destination node of the packet transmission, wherein the number of relay nodes is an estimate of a number of relay nodes in the packet transmission at a last hop;
• and
• a third circuit of the source node that is configured to set a size of the RACH area based on a comparison of the estimates of the number of nodes of the second hop and the number of nodes at the destination stage,
• wherein the source node transmits a packet having a RACH area at the determined size.

A method to dynamically allocate a size of a RACH area of a packet, comprising:

• listening, by a source node of a multihop network, a RACH area during a packet transmission at a second hop;
• estimating, by the source node of the multihop network, a number of relay nodes at the second hop by detecting those subcarriers listed in the RACH area whose energy content crosses a preset threshold;
• receiving, by the source node, a number of relay nodes at a destination stage transmitted by a destination node of the packet transmission, wherein the number of relay nodes is an estimate of a number of relay nodes in the packet transmission at a last hop;
• determining, by the source node, a size of the RACH area based on a comparison of the estimates of the number of nodes of the second hop and the number of nodes at the destination stage;
• and
• transmitting, by the source node, a packet having a RACH area at the determined size across the multihop network.

A relay of a multihop network, comprising:

• a first circuit of a relay node that scans subcarriers in a RACH area to estimate a number of previous hop relays by detecting those subcarriers listed in the RACH area whose energy content crosses a preset threshold;
• a second circuit of the relay node that receives a packet including a hop number corresponding to a current number of times that the packet has been transmitted on a path towards a destination node;
• and
• a third circuit of the relay node that sets a transmit power level for the relay node based on the estimate of the number of previous hop relays and the hop number.

A method for open-loop transmit power control, comprising:

• scanning, by a relay node in a multihop network, subcarriers in a RACH area;
• detecting those subcarriers listed in the RACH area whose energy content crosses a preset threshold;
• estimating, by the relay node, a number of previous hop relay nodes based on a number of those subcarriers whose energy content crosses the preset threshold;
• receiving, by the relay node, a packet including a hop number corresponding to a current number of times that the packet has been transmitted on a path towards a destination node;
• determining, by the relay node, a value of a transmit power level based on the estimate of the number of previous hop relay nodes and the hop number;
• and
• setting, by the relay node, the transmit power level of the relay node to the determined value.