METHOD AND SYSTEM OF BI-DIRECTIONAL TRANSMISSION TO IMPROVE UPLINK PERFORMANCE

Abstract

In coverage enhancement of machine type communication (MTC), a downlink transmitted bit stream is jointly encoded with uplink payload by the terminal. The combined signal is sent on uplink, to be jointly decoded by the base station that knows the downlink payload and the joint encoding mechanism at the mobile terminal.

Claims

1-20. (canceled)

21. A method of wireless communication comprising, transmitting, by a base station to at least one of a plurality of terminals, a downlink message comprising user-specific information to individual ones of the plurality of terminals; receiving, by the base station from the at least one of the plurality of terminals, an uplink message encoded jointly with at least some of information in the downlink message; and decoding the uplink message based on the downlink message.

22. The method of claim 21, wherein the user-specific information comprises at least one of a payload size, a modulation order, a bit rate, a signal format, a channel coding, or a time-frequency resource that is different the individual ones of the plurality of terminals.

23. The method of claim 21, wherein the uplink message is encoded jointly based on performing a bitwise exclusive or operation on information in the downlink message and information in the uplink message.

24. The method of claim 21, wherein the plurality of terminals comprises machine type communication (MTC) devices.

25. A wireless communication device, comprising: a transmitter configured to transmit, to at least one of a plurality of terminals, a downlink message comprising user-specific information to individual ones of the plurality of terminals; a receiver configured to receive, from the at least one of the plurality of terminals, an uplink message encoded jointly with at least some of information in the downlink message; and a processor configured to decode the uplink message based on the downlink message.

26. The device of claim 25, wherein the user-specific information comprises at least one of a payload size, a modulation order, a bit rate, a signal format, a channel coding, or a time-frequency resource that is different the individual ones of the plurality of terminals.

27. The base station of claim 25, wherein the uplink message is encoded jointly based on performing a bitwise exclusive or operation on information in the downlink message and information in the uplink message.

28. The base station of claim 25, wherein the plurality of terminals comprises machine type communication (MTC) devices.

29. A method of wireless communication, comprising: receiving, by a terminal from a base station, a downlink message that is user-specific to the terminal; encoding an uplink message jointly with at least some of information in the downlink message; and transmitting the uplink message that is jointly encoded to the base station.

30. The method of claim 29, wherein at least one of a payload size, a modulation order, a bit rate, a signal format, a channel coding, or a time-frequency resource of the downlink message is user-specific to the terminal.

31. The method of claim 29, wherein encoding comprises performing a bitwise exclusive or operation on information in the downlink message and information in the uplink message.

32. The method of claim 29, wherein the terminal comprises a machine type communication (MTC) device.

33. A wireless communication device, comprising: a receiver configured to receive, from a base station, a downlink message that is user-specific to the terminal; an encoder configured to encode an uplink message jointly with at least some of information in the downlink message; and a transmitter configured to transmit, to the base station, the uplink message that is jointly encoded.

34. The device of claim 33, wherein at least one of a payload size, a modulation order, a bit rate, a signal format, a channel coding, or a time-frequency resource of the downlink message is user-specific to the terminal.

35. The device of claim 33, wherein the encoder is configured to encode the uplink message jointly based on performing a bitwise exclusive or operation on information in the downlink message and information in the uplink message.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0016] The above and other aspects, features, and advantages of the present invention may be more apparent from the following more particular description of embodiments thereof, presented in conjunction with the following drawings. In the drawings:

[0017] FIG. 1 illustrates the downlink stage.

[0018] FIG. 2 illustrates the uplink stage.

[0019] FIG. 3 is a flowchart.

DETAILED DESCRIPTION

[0020] A better understanding of various features and advantages of the present methods and devices may be obtained by reference to the following detailed description of illustrative embodiments of the invention and accompanying drawings. Although these drawings depict embodiments of the contemplated methods and devices, they should not he construed as foreclosing alternative or equivalent embodiments apparent to those of ordinary skill in the subject art.

[0021] Referring to the accompanying drawings, and initially mainly to FIGS. 1 and 2, there is illustrated an example of integrating downlink bearing bits and an uplink pay load and jointly encoding the downlink bits and the uplink bits to form a combined bit stream to be sent in the uplink.

[0022] The present method and devices apply a principle of network coding where bit streams coming from different nodes can be added together to improve the overall system capacity. Such principle is particularly applied in a scenario of machine type communication (MTC) where coverage requirements can be very challenging, especially for an uplink that is limited by the maximum transmitting power and the number of antennas at the terminals. The situation can be aggravated because uplinking terminals may be devices such as utility meters installed in basements, from which good transmission is difficult to obtain. The situation of the downlink tends to be less difficult, because the base stations can easily have higher transmitting power and a larger number of antennas than the terminals. Hence, some link budget imbalance between downlink and uplink can be compensated by jointly decoding the downlink and uplink signals.

[0023] In the example shown in FIGS. 1 and 2, only two terminals are shown, in the form of mobile stations denoted as user equipment UE1 and UE2, respectively. However, there may be more or fewer terminals, and some or all of the terminals may be stationary rather than mobile.

[0024] Referring now also to FIG. 3, during a downlink transmission stage, the base station sends signals bearing information bit streams d1 and d2 to terminals UE1 and UE2, respectively. These two streams can in general be different, which means that they can be encoded and modulated with different code rates and modulation order, and then transmitted to each HE with dedicated resources. This provides the freedom to adjust the downlink transmission payload individually to each mobile station. Since uplink quality of each mobile station may be different, the optimum size and content of the downlink payload to participate the joint coding may be different for different uplink connections.

[0025] Alternatively, bit streams d1 and d2 can be the same, so that the base station can broadcast to both UE1 and UE2, using the code rate, modulation, and radio resources common to them. While the broadcast transmission has less flexibility in controlling the downlink data rate per link, it has less overhead and may be preferable in some scenarios. In a larger system with many terminals UE1, UE2, . . . , some or all of the terminals may be organized in groups with a common transmission to all the terminals in a group, and different transmissions to terminals not in the same group.

[0026] When a terminal UE1 or UE2 successfully decodes the respective bit stream d1 or d2, the terminal then encodes its own uplink payload, u1 or u2, respectively, jointly with the respective downlink payload d1 or d2, to form an uplink payload f(d, u). The joint coding can be a type of network coding. A very simple of such joint coding can be an exclusive or operation on each bit of d and u. In this case, the length of d used in the coding is the same as the length of u. Consequently, the jointly coded bit stream has the same length as the terminal's own uplink payload. If the length of the uplink payload is known in advance, then a downlink payload d of the correct length may be supplied. Alternatively, or if a common downlink payload is used by two or more terminals having uplink payloads of different lengths, the downlink payload may be truncated or repeated to provide a bit stream of the correct length. Alternatively, a more sophisticated joint coding may be used and the resulted bit stream may be longer than the mobile's own uplink payload.

[0027] At the base station's receiver, the uplink message is decoded. The decoder takes account of the downlink transmitted bit stream d, which is of course already known to the decoder. The decoder also uses the knowledge of the joint coding mechanism at the terminal's transmitter, which is agreed in advance or specified in the air-interface specifications. The decoding is then performed in joint manner, where d also participates the decoding of u.

[0028] Many modifications and alterations of the methods and systems described herein may be employed by those skilled in the art without departing from the spirit and scope of the invention which is limited only by the claims.