Intelligent packet repetition in mobile satellite service (MSS) links to overcome channel blockages
Systems and methods for intelligent packet repetition in mobile satellite service links to overcome channel blockages. One example method includes transmitting and receiving packetized wireless communications between first and second communications devices via a bidirectional wireless link. The method includes receiving, by a first communications device from a second communications device, feedback information including an indication of a blockage in the communication channel, the indication including information indicating the presence and extent of the blockage, wherein the feedback does not include status indications for individual received packets. The method includes, responsive to receiving the indication of a blockage in the communication channel, determining a packet repeat value based on the feedback information, wherein the packet repeat value may be greater than one. The method includes modifying a transmit signal of the bidirectional wireless link to repeat transmitted packets based on the packet repeat value.
1. A wireless communications system comprising:
a base station; and
a user equipment;
wherein:
the base station and the user equipment are configured to transmit and receive wireless communications via a bidirectional wireless link including a downlink signal, an uplink signal, and a plurality of narrowband spread spectrum reference signals; and
the user equipment is configured to:
receive the plurality of narrowband spread spectrum reference signals;
estimate a signal strength by combining the plurality of narrowband spread spectrum reference signals over multiple symbols;
estimate a propagation channel excess pathloss of the downlink signal based on the signal strength;
encode the propagation channel excess pathloss to a quantized deficit value by using a single binary digit; and
communicate the quantized deficit value to the base station.
2. The system of claim 1 , wherein the propagation channel excess pathloss corresponds to a plurality of states of the downlink signal.
3. The system of claim 2 , wherein the plurality of states comprises an ordered list from a relatively low excess path loss to a relatively high excess path loss.
4. The system of claim 3 , wherein the plurality of states is restricted to transition between states sequentially according to their order.
5. The system of claim 1 , wherein the user equipment is further configured to combine the plurality of narrowband spread spectrum reference signals over multiple symbols by coherently combining the plurality of narrowband spread spectrum reference signals over frequency-domain elements and time-domain elements.
6. The system of claim 1 , wherein the user equipment is further configured to generate the single binary digit using a process of binary sequential encoding.
7. The system of claim 1 , wherein the base station is further configured to:
determine packet repeat values for at least a first and second packet type, based on the quantized deficit value;
modify the downlink signal of the bidirectional wireless link to repeat transmitted packets based on their packet repeat values corresponding to their packet types; and
transmit the downlink signal using the packet repeat values, wherein the packet repeat values are indicative of the numbers of packet repetitions necessary to enable the user equipment to receive the transmitted packet types with adequate reliability by packet combining.
8. The system of claim 7 wherein, for the first packet type, the packet repeat value is not explicitly communicated by the base station to the user equipment before the packet repetition is commenced, whereas for the second packet type, the corresponding repeat value is transmitted to the user equipment before the packet repetition is commenced.
9. The system of claim 8 , wherein the user equipment is further configured to:
unilaterally determine an expected packet repeat value for the first packet type;
determine an expected time of arrival at the user equipment of the first packet type; and
begin processing a received packet of the first packet type at the expected time of arrival on the assumption that the received packet will be repeated a number of times corresponding to the expected packet repeat value.
10. The system of claim 9 , wherein the user equipment is further configured to determine the expected time of arrival at the user equipment of the first packet type based on a timer, whose period includes an expected round trip propagation delay and an expected base station processing delay.
11. The system of claim 1 , wherein the user equipment is further configured to:
receive from the base station an indication of the packet repeat value to be used on the uplink;
modify the uplink signal of the bidirectional wireless link to repeat transmitted packets based on their packet repeat value; and
transmit the uplink signal using the packet repeat values.
12. A method for operating a wireless communications system including a base station and a user equipment configured to transmit and receive wireless communications via a bidirectional wireless link including a downlink signal and an uplink signal, the method comprising:
receiving, by the user equipment, a plurality of narrowband spread spectrum reference signals transmitted by the base station;
estimating a signal strength by combining the plurality of narrowband spread spectrum reference signals over multiple symbols;
estimating a propagation channel excess pathloss of the downlink signal based on the signal strength;
encoding the propagation channel excess pathloss to a quantized deficit value by using a single binary digit; and
communicating the quantized deficit value from the user equipment to the base station.
13. The method of claim 12 , wherein the propagation channel excess pathloss corresponds to a plurality of states of the downlink signal.
14. The method of claim 13 , wherein the plurality of states comprises an ordered list from a relatively low excess path loss to a relatively high excess path loss.
15. The method of claim 14 , wherein the plurality of states is restricted to transition between states sequentially according to their order.
16. The method of claim 12 , wherein combining the plurality of narrowband spread spectrum reference signals over multiple symbols includes coherently combining the plurality of narrowband spread spectrum reference signals over frequency-domain elements and time-domain elements.
17. The method of claim 12 , wherein generating the single binary digit includes generating the single binary digit using a process of binary sequential encoding.
18. The method of claim 12 , further comprising:
determining packet repeat values for at least a first and second packet type, based on the quantized deficit value;
modifying the downlink signal of the bidirectional wireless link to repeat transmitted packets based on their packet repeat values corresponding to their packet types; and
transmitting the downlink signal using the packet repeat values, wherein the packet repeat values are indicative of the numbers of packet repetitions necessary to enable the user equipment to receive the transmitted packet types with adequate reliability by packet combining.
19. The method of claim 18 wherein, for the first packet type, the packet repeat value is not explicitly communicated by the base station to the user equipment before the packet repetition is commenced, whereas for the second packet type, the corresponding repeat value is transmitted to the user equipment before the packet repetition is commenced.
20. The method of claim 19 , further comprising:
unilaterally determining, with the user equipment, an expected packet repeat value for the first packet type;
determining an expected time of arrival at the user equipment of the first packet type;
and beginning processing of a received packet of the first packet type at the expected time of arrival on the assumption that the received packet will be repeated a number of times corresponding to the expected packet repeat value.
21. The method of claim 20 , wherein determining the expected time of arrival at the user equipment of the first packet type is based on a timer, whose period includes an expected round trip propagation delay and an expected base station processing delay.
22. The method of claim 12 , further comprising:
receiving from the base station an indication of the packet repeat value to be used on the uplink;
modifying the uplink signal of the bidirectional wireless link to repeat transmitted packets based on their packet repeat value; and
transmitting the uplink signal using the packet repeat values.