Multi-hop wireless communications system and method
View Patent ↗A multi-hop wireless, for example cellular, communications system is provided comprising a source equipment which may be one of a base station or an end user terminal for transmitting signals towards a destination equipment which may be the other of a base station or an end user terminal via at least one relay equipment. The relay equipment receives a plurality of signals transmitted from one or more source equipments of the system and from this plurality of signals selects a signal to relay. In this way the decision about which relays are included in which communication paths in the system is distributed to the relay equipments of the system, thus reducing the signalling overhead as compared with link state protocols which are typically used for routing in such multi-hop systems.
1. A multi-hop wireless communications system comprising a plurality of relay equipments and a destination equipment, in which uplink signals may be relayed from at least one source equipment towards the destination equipment via at least one of said plurality of relay equipments, corresponding downlink signals may be relayed from the destination equipment towards the at least one source equipment via at least one of said plurality of relay equipments, and the destination equipment comprises an adaptive antenna array arranged to transmit said corresponding downlink signals,
wherein each of said plurality of relay equipments measures the quality of uplink signals received from the at least one source equipment and measures the quality of downlink signals received at the relay equipment from the destination equipment and selects, based on the quality of the received uplink signals and the quality of the received downlink signals forming duplex communication with the uplink signals, an uplink signal to relay, and
wherein, responsive to a determination of received signal strength of each selected uplink signal at the destination equipment, the adaptive antenna array is arranged to form a beam pattern, whereby to preferentially receive uplink signals from and preferentially transmit downlink signals towards at least one of said plurality of relay equipments that relays one of the selected uplink signals determined to have the strongest received signal strength at the destination equipment.
2. A communications system according to claim 1 , wherein the at least one source equipment is an end user terminal and the destination equipment is a base station.
3. A communications system according to claim 1 , wherein each of said plurality of relay equipments measures the quality of each uplink signal and each downlink signal it receives, compares the quality measured for each uplink signal to a threshold quality for that uplink signal and compares the quality measured for each downlink signal with a threshold quality for that downlink signal, and rejects any received uplink signals and any received downlink signals of a quality below the respective threshold.
4. A communications system according to claim 1 , wherein each of said plurality of relay equipments measures the quality of each uplink signal it receives and selects the uplink signal having the best measured quality.
5. A communications system according to claim 1 , wherein each of said plurality of relay equipments measures the quality of each uplink signal it receives, compares the quality measured for each uplink signal to a threshold quality for that signal, forms a candidate set of uplink signals comprising those received uplink signals having a quality above the threshold and selects one of the candidate set of uplink signals.
6. A communications system according to claim 1 , wherein each of said plurality of relay equipments comprises a signal processor for measuring the quality of each uplink signal received from the at least one source equipment, for comparing the quality measured for each uplink signal to a threshold quality for that uplink signal, for forming a candidate set of uplink signals comprising those received uplink signals having a quality above the threshold, for measuring the quality of each downlink signal received from the destination equipment, for comparing the quality measured for each downlink signal to a downlink threshold quality for that downlink signal, for forming a candidate set of downlink signals comprising those received downlink signals having a quality above the downlink threshold and for selecting that uplink signal of the candidate set of uplink signals having the biggest difference between its measured quality and its threshold quality whose corresponding downlink signal is a member of the candidate set of downlink signals, wherein each of said plurality of relay equipments relays the selected uplink signal towards the destination equipment.
7. A communications system according to claim 1 , wherein each of said plurality of relay equipments comprises a signal processor for measuring the quality of each downlink signal received from the destination equipment, comparing the quality measured for each downlink signal to a threshold quality for that downlink signal, for forming a candidate set of downlink signals comprising those received downlink signals having a quality above their associated thresholds, for forming a candidate set of uplink signals comprising those received uplink signals having a quality above their threshold and for selecting that downlink signal of the candidate set of downlink signals whose corresponding uplink signal is a member of the candidate set of uplink signals having the biggest difference between its measured quality and its threshold quality, wherein each of said plurality of relay equipments relays the selected downlink signal towards the at least one source equipment.
8. A communications system according to claim 1 , wherein in relation to the selected uplink signal each of said plurality of relay equipments increases the power of the uplink signal it transmits relative to the uplink signal it receives by an amount dependent on the measured quality of the selected uplink signal.
9. A communication system according to claim 1 , wherein each of said plurality of relay equipment is an end user equipment.
10. A communication system according to claim 1 , comprising a power control arrangement according to which the power of the uplink signal transmitted by the at least one source equipment is dependent on a power control instruction received from the destination equipment.
11. A communications system according to claim 1 , wherein the at least one source equipment is a base station and the destination equipment is an end user terminal.
12. A method in a multi-hop wireless communications system of relaying an uplink signal from at least one source equipment towards a destination equipment and relaying a corresponding downlink signal from the destination equipment to the at least one source equipment via at least one relay equipment, wherein the communications system comprises a plurality of relay equipments and the destination equipment, and the destination equipment comprises an adaptive antenna array, the method comprising the steps of:
each of said plurality of relay equipments receiving a plurality of uplink signals from the at least one source equipment and receiving downlink signals from the destination equipment,
each of said plurality of relay equipments measuring the quality of the uplink and downlink signals it receives and selecting, based on the quality of the received uplink signals and the quality of the received downlink signals forming duplex communication with the uplink signals, an uplink signal to relay; and
using the adaptive antenna array at the destination equipment to form a beam pattern in response to a determination of received signal strength of each selected uplink signal at the destination equipment, whereby to preferentially receive uplink signals from and to preferentially transmit downlink signals towards one of the relay equipments that relays one of the selected uplink signals determined to have the strongest received signal strength at the destination equipment.
13. A method according to claim 12 , wherein the source equipment is an end user terminal and the destination equipment is a base station.
14. A method according to claim 12 , comprising the steps of, each of said plurality of relay equipments:
measuring the quality of each uplink signal it receives;
comparing the quality measured for each uplink signal to a threshold quality for that uplink signal; and
rejecting those received uplink signals of a quality below the threshold.
15. A method according to claim 12 , comprising the steps of, each of said plurality of relay equipments:
measuring the quality of each uplink signal it receives; and
selecting the uplink signal having the best measured quality.
16. A method according to claim 12 , comprising the steps of, each of said plurality of relay equipments:
measuring the quality of each uplink signal it receives;
comparing the quality measured for each uplink signal to a threshold quality for that uplink signal;
forming a candidate set of uplink signals comprising those received uplink signals having a quality above the respective threshold; and
selecting an uplink signal from the candidate set of uplink signals.
17. A method according to claim 12 , comprising the steps of, each of said plurality of relay equipments:
measuring the quality of each uplink signal it receives from the at least one source equipment;
comparing the quality measured for each uplink signal to a threshold quality for that uplink signal;
forming a candidate set of uplink signals comprising those received uplink signals having a quality above the threshold;
measuring the quality of each downlink signal it receives from the destination equipment;
comparing the quality measured for each downlink signal to a downlink threshold quality for that downlink signal;
forming a candidate set of downlink signals comprising those received downlink signals having a quality above their thresholds;
selecting that uplink signal of the candidate set of uplink signals having the biggest difference between its measured quality and its threshold quality whose corresponding downlink signal is a member of the candidate set of downlink signals; and
relaying that selected uplink signal towards the destination equipment.
18. A method according to claim 12 , comprising the steps of, each of said plurality of relay equipments:
measuring the quality of each downlink signal it receives from the destination equipment;
comparing the quality measured for each downlink signal to a threshold quality for that downlink signal;
forming a candidate set of downlink signals comprising those received downlink signals having a quality above the threshold;
forming a candidate set of uplink signals received from the at least one source equipment having a quality above their threshold;
selecting that downlink signal of the candidate set of downlink signals whose corresponding uplink signal is a member of the candidate set of uplink signals having the biggest difference between its measured quality and its threshold quality; and
relaying that selected downlink signal towards the destination equipment.
19. A method according to claim 12 , comprising the additional step of each of said plurality of relay equipments, in relation to the selected uplink signal, increasing the power of the uplink signal it transmits relative to the uplink signal it receives by an amount dependent on the measured quality of the selected uplink signal.
20. A method according to claim 12 , comprising making the power of the uplink signal transmitted by the at least one source equipment dependent on a power control instruction received from the destination equipment.
21. A method according to claim 12 , wherein the at least one source equipment is a base station and the destination equipment is an end user terminal.