A computer implemented method for determining a size of a local peer group, LPG, network within a dynamic mobile environment, the LPG network comprising a plurality of wireless mobile nodes arranged in a mesh network, the plurality of mobile nodes in the LPG network including a first node for transmitting a heartbeat signal to the other nodes in the LPG network, the method comprising the steps of: transmitting a heartbeat signal from the first node to a second node, the second node being one of the other nodes in said plurality of mobile nodes of the LPG network; receiving the heartbeat signal at the second node; transmitting a message response from the second node to the first node in response to receiving the heartbeat signal; measuring a roundtrip time (T R)between the first node and the second node, wherein T R = T H + T M; wherein T H is the time taken for transmitting the heartbeat signal from the first node to the second node, and T M is the time taken for transmitting the message response from the second node to the first node in response to receiving the heartbeat signal, wherein the message response comprises a node identifier and a hop count value for the second node; utilizing a look up table that specifies in a first dimension a plurality of LPG network size values in increasing order, and that specifies in a second dimension a plurality of hop count values in increasing order; populating the lookup table with the measured roundtrip time (T R), wherein the roundtrip time is associated with the respective hop count value in the second dimension of the lookup table that corresponds to the hop count value in the message response, and is populated in the lookup table in increasing order in the first dimension of the lookup table; wherein, the computer performs the steps of measuring, utilizing and populating for each of the plurality of other nodes in the LPG network; estimating one or more additional roundtrip times from the roundtrip time; completing the lookup table with the one or more additional roundtrip times; the method further comprising: selecting the size of the LPG network utilizing the round trip time (T R) for each of the other nodes and the estimated additional roundtrip times from the lookup table; said selecting further comprising, determining the LPG network size value by determining the number of nodes associated with a measured or estimated round trip time(T R) that is less than a predetermined threshold time value and a hop count value that is less than a predetermined maximum allowable hop count value. transmitting a heartbeat signal from the first node to a second node, the second node being one of the other nodes in said plurality of mobile nodes of the LPG network; receiving the heartbeat signal at the second node; transmitting a message response from the second node to the first node in response to receiving the heartbeat signal; measuring a roundtrip time (T R)between the first node and the second node, wherein T R = T H + T M; wherein T H is the time taken for transmitting the heartbeat signal from the first node to the second node, and T M is the time taken for transmitting the message response from the second node to the first node in response to receiving the heartbeat signal, wherein the message response comprises a node identifier and a hop count value for the second node; utilizing a look up table that specifies in a first dimension a plurality of LPG network size values in increasing order, and that specifies in a second dimension a plurality of hop count values in increasing order; populating the lookup table with the measured roundtrip time (T R), wherein the roundtrip time is associated with the respective hop count value in the second dimension of the lookup table that corresponds to the hop count value in the message response, and is populated in the lookup table in increasing order in the first dimension of the lookup table; wherein, the computer performs the steps of measuring, utilizing and populating for each of the plurality of other nodes in the LPG network; estimating one or more additional roundtrip times from the roundtrip time;