HK1082136B - A real-time control mechanism for multi-rate data transmissions in wireless networks - Google Patents

Description

Real-time rate control mechanism for multi-rate data transmission in wireless networks

Technical Field

The present invention relates to data transmission in a communication network, and more particularly, to a method and system for data transmission in a network, wherein receivers of the network have different data reception rate capabilities.

Background

Multi-rate capabilities are increasingly becoming a necessity for wireless data networks. For example, to be competitive, and to implement a flexible sales strategy, a network service provider may need to be able to offer customers different data rates at different prices.

Furthermore, as technology advances, vendors and service providers can periodically offer customers a new generation of improved receiving equipment. This leads to a situation where some network users may have the newest equipment with the highest data reception rate capability, while other network users who are not willing to bear the upgrade costs may have older equipment with a lower data reception rate capability.

More generally, for various reasons, future wireless networks will tend to become increasingly heterogeneous in terms of processing power of the user receiving device.

Known data transmission methods in wireless networks either do not allow for differences in data reception rate capabilities between users or typically handle such differences efficiently when they exist. In particular, this data transfer method may waste bandwidth because the data transfer rate must be adapted to the user having the slowest device.

In view of the foregoing, there is a need for a method and system for efficiently handling data transmissions in a wireless network where users have different data reception rate capabilities.

Disclosure of Invention

In accordance with an embodiment of the present invention, in a communication network including a plurality of receivers having different data reception rate capabilities, data frames targeted for each receiver may be transmitted to each receiver in accordance with the respective data reception rate capabilities of each receiver.

In one embodiment, a queue of data frames targeted to each receiver may be maintained, and data frames to be transmitted may be selected from the queue based on the data reception rate capability of the targeted receiver of the selected data frames. To select a data frame, the data reception rate capability of the target receiver of the queued frame may be identified. The queued data frames may be transmitted to the target receiver if the data reception rate capability of the target receiver is not exceeded by transmitting the queued data frames in the next consecutive channel resource slot. Otherwise, the queue must be searched to find a data frame that can be transmitted in the next channel resource slot without exceeding the data reception rate capability of its target receiver.

Drawings

FIG. 1 shows an example of a wireless network configuration in which users have different data reception rate capabilities;

fig. 2 is a block diagram of an embodiment of a base station and a rate controller in accordance with the present invention;

3A-3C illustrate an example of rate control according to one embodiment of the present invention; and

fig. 4 is a flow chart illustrating rate control according to one embodiment of the present invention.

Detailed Description

According to embodiments of the present invention, a rate controller that efficiently controls data transmission to different data reception rate capabilities may be embedded in a base station of a wireless network. Fig. 1 shows one possible configuration of such a wireless communication network. In fig. 1, m network users 101 may receive wireless transmissions 102 from one base station 100 of a wireless network. User 101 is at a fixed location, such as a private residence or office as shown in fig. 1, but it should be understood that the present invention is not limited to fixed users, but also includes mobile users.

User 1 through user m may, for example, download information from an information source such as the internet 104. The information is typically in the form of data "frames" (also referred to as "packets"), each having a header that can be used to route the data frame through the network to a target user in a point-to-point manner according to some data protocol, such as TCP/IP (transmission control protocol/internet protocol). The downloaded information may be transmitted to the base station 100, for example, via a wired or wireless link.

Each user 1-m has a different data reception rate capability. More specifically, each user may have a receiving device (referred to herein as a "receiver") with a different data reception rate capability than the other users. A typical receiver 105 may be implemented as a modular unit that may be installed in a place or outside an office. A typical receiver may include one or more processors and a receive antenna. In known receivers, the data reception rate capability may vary between, for example, 512 bits/sec and 2.5 mbits/sec, depending on factors such as processing speed.

In the example shown in fig. 1, the transmission bandwidth of the base station 100 (or more specifically, the transmitter thereof) is R bits/second. Therefore, in order to have the data receiving rate capability R respectively₁、R₂、R₃、...、R_mM receivers 105 of bits/second serve (where, for example, the condition is satisfied: R₁＜R＜R₃、...＜R_m) R may be equal to R₁+R+R₃+...+R_m. It should of course be understood that not all receivers of a given network need to have different data reception rate capabilities in accordance with embodiments of the present invention; more specifically, some receivers of the network may have the same data reception rate capability.

It should also be understood that "data reception rate capability" as used herein refers not only to limitations of receiver technology such as processing speed, but also to constraints that may be imposed arbitrarily on the transmission data rate (e.g., according to pricing agreements with the user).

Fig. 2 shows more details of the components of the transmitter 210 of the base station 100 according to an embodiment of the invention. The source encoder 201, channel encoder 202, digital modulator 204 and transmitter 205 are conventional and will not be discussed in detail here. Briefly, a local data source 200 may provide data to a source encoder 201 of a base station 100. The source encoder 201 may process data from a data source 200 to map source symbols in the data to an intermediate alphabet, typically a set of binary strings, and pass the processed data to the channel encoder 202. The channel encoder 202 may map data received from the source encoder 201 into a set of coded bits or waveforms for transmission over a channel, performing operations such as adding error detection and check bits to the data. The rate controller 203 according to the present invention may then process the data as described in more detail below. The rate controlled data generated by rate controller 203 may then be input to digital modulator 204, which modulator 204 may modulate the data according to some digital modulation scheme, such as QAM (quadrature amplitude modulation). The modulated data may then be transmitted by the antenna 205 over a wireless channel to a plurality of receivers 105.

The transmitter 210 of the base station 100 may comprise computing resources such as a computer processor, memory, storage media such as a disk, and software for processing data as described above. These computational resources and associated channel bandwidths are collectively referred to herein as "transmitter resources". Because the channel bandwidth is available to transmit data to multiple users, the transmitter resources may be multiplexed using some multiplexing scheme. In such a multiplexing scheme, the available bandwidth of a channel may be divided into "channel resource slots". The execution channel resource slots may be time slots, frequency slots, or frequency-time slots. For example, the available channel resource slots may be divided into time slots according to well-known Time Division Multiplexing (TDM) techniques, where each bandwidth time slice is allocated to a different user. Other multiplexing schemes that may be employed in accordance with the present invention include frequency division multiplexing and frequency-time division multiplexing.

As previously described, multiple users 101 may download information from the internet 104 or other data source, resulting in multiple data frames targeted to multiple receivers 105 to the transmitter 210 of the base station 100. After being processed by the source encoder 201 and the channel encoder 202 as described above, data frames targeted to respective receivers may be processed by the rate controller 203 according to the present invention. It should be understood that typical digital communication systems are not multi-rate and therefore do not have a rate controller 203 as shown. Rate controller 203 may include a frame buffer 206 in which a queue 208 of targeted data frames received from a channel encoder is maintained. Rate controller 203 may also include a frame selector 207.

As previously described, the transmitter 210 of the base station 100 may include a computer processor, memory, storage, and software to implement its functions. In particular, the frame selector 207 may be implemented with computer-executable instructions, while the frame buffer 206 containing the queue 208 may be maintained in a memory of the transmitter. Frame buffer 206 should be formatted, for example, as an array or linked list.

The frame selector 207 may be configured to select a data frame from the queue 208 for transmission, depending on the data reception rate capability of the target receiver for the selected data frame. To select a data frame, the data reception rate capability of the target receiver of the queued frame may be identified. The queued data frame may be transmitted to the target receiver if the data reception rate capability of the target receiver is not exceeded by transmitting the queued data frame in the next consecutive channel resource slot. Otherwise, the queue may be searched to find a data frame that can be transmitted in the next channel resource slot without exceeding the data reception rate capability of its target receiver.

Figures 3A-3C illustrate one example of the foregoing. For ease of understanding, an example is discussed in which the channel resource slots are time slots. However, it should be understood that a channel resource slot may also be a frequency slot or a frequency-time slot.

In fig. 3A, a sequence 300 of data frames 301 is shown. "A", "B" and "C" indicate the respective data frame intended receivers, i.e., receiver A is frame A₁-A₁₀Receiver B is frame B₁-B₅And receiver C is frame C₁-C₅The destination of (2). The subscripts indicate the order in which the data frames are transmitted to the respective receivers.

Typically, data frames will arrive at the base station 100 in "bursts", as shown: i.e. in the form of groups of consecutive frames targeted to one receiver. In the example shown in fig. 3A, a certain burst length is 5 frames; two bursts are targeted to receiver a and one burst is targeted to receivers B and C.

In this example, it is assumed that the base station 100 can transmit data at a maximum rate of 1 frame per second. Also, it is assumed that each second corresponds to one time slot of a channel resource slot. Further, assume that receiver a has a data reception rate capability of 1 frame per 5 seconds; b has a data reception rate capability of 2 frames per 5 seconds; and C has a data reception rate capability of 3 frames per 5 seconds.

Fig. 3B illustrates how a frame may be transmitted to its corresponding target receiver without a rate controller according to the present invention. The "oldest" frame, i.e., the frame with the longest queuing time, should be transmitted first. Therefore, frame a is first transmitted₁-A₅. However, because receiver A has a data reception rate capability of 1 frame per 5 seconds, base station 100 must be transmitting frame A₁Thereafter, frame A is transmitted₂It is waited for 4 seconds before, otherwise the data reception rate capability of receiver a would be exceeded. Thus, 4 time slots of channel resource slots are wasted. Similarly, at each A₃、A₄And A₅4 slots are wasted between transmissions.

Frame B in turn₁-B₅When transmitted to receiver B, two frames may be transmitted in consecutive time slots as shown. However, since the data reception rate capability of receiver B is only 2 frames per 5 seconds, soIn B₂、B₃、B₄And B₅3 slots are wasted between transmissions.

The data reception rate capability of receiver C is 3 frames per 5 seconds, so 3 frames targeted for receiver C can be transmitted in 3 consecutive time slots. However, as shown, 2 slots are wasted.

Finally, 4 more slots per frame are wasted in transmitting the second burst targeted to receiver a.

Fig. 3C illustrates, by way of comparison, transmission of a sequence 300 using a rate control method according to an embodiment of the present invention. Assume that sequence 300 has been queued in frame buffer 206. Likewise, the oldest frame is sent first. Therefore, frame a is transmitted first as described previously₁But then determines that transmitting frame a2 in the next consecutive time slot will exceed the data reception rate capability of receiver a. Thus, the queue 208 in the frame buffer 206 is searched to find a data frame that can be transmitted in the next consecutive time slot without exceeding the data reception rate capability of its target receiver. In this example, B₁The next frame in queue 208 that can be transmitted in the next consecutive time slot without exceeding the data reception rate capability of its target receiver. Thus, in the following A₁Intra-slot transmission of frame B₁Without inserting free slots. Likewise, may be in the immediate vicinity of B₁Intra-slot transmission of frame B₂Without exceeding the data reception rate capability of receiver B.

However, since the data reception rate capability of receiver B is only 2 frames per 5 seconds. So that it cannot follow frame B₂Intra-slot transmission of frame B₃. Thus, the queue 208 in the frame buffer 206 is searched to find a data frame that can be transmitted in the next consecutive time slot without exceeding the data reception rate capability of its target receiver.

Thus, frame C is then selected₁To be transmitted. Frame C₁In the next frame B₂Transmitting within a slot of a time slot without inserting a free time slot. Likewise, frame C may be immediately followed₁Intra-slot transmission of frame C of a slot₂。

Then, since the slave frame A₁4 time slots have elapsed since transmission, so can now be in the immediate C₂The oldest frame a in the transmit queue 208 within a slot of a timeslot₂. However, frame A cannot be transmitted next₃Thus, by associating frame B as above₁、B₂、C₁And C₂The same decision is made as described, in frame A₂Transmitting frame B in 4 consecutive time slots after the time slot₃、B₄、C₃And C₄。

Then, since the slave frame A₂4 time slots have elapsed since transmission, so can now be in the immediate C₄Intra-slot transmission of frame A₃. Frame B is then transmitted in the next two consecutive time slots₅And C₅。

Finally, frame A is sent₄、A₅And A₆. In this particular example, an unrefreshed queue is discussed, so that idle slots occur in frame C₅And A₄Between time slots of, and frame a₅And A₆Between time slots of (a). In practice, new data frames will be continuously fed to the frame buffer 206 and added to the queue 208, whereby a large number of such free time slots will not occur.

Fig. 4 illustrates the foregoing process in flow chart form. The flow chart illustrates the process on a per slot basis, i.e. the process determines for a given slot whether a frame can be sent or whether idle slots are necessary.

The process begins with the oldest frame in the queue 208, as shown in oval 400. As shown in block 401, a determination is made whether the frame can be transmitted to its target receiver in the next consecutive time slot of the channel resource slot without exceeding the data reception rate capability of the target receiver. To implement this step, the data reception rate capability of the target receiver may be included in the frame header, according to one embodiment. Alternatively, the data reception rate capability of each receiver in the network may be contained in a look-up table accessible by the frame selector 207. After determining the data reception rate capability of the target receiver, the frame selector 207 may compare it to a running count of how many frames have been sent to the target receiver in the past N consecutive time slots, where N is some suitably selected, user-dependent number.

If the data reception rate capability of the target receiver is not exceeded, the frame may be transmitted to the target receiver, as shown in block 402.

However, if the data reception rate capability of the target receiver is exceeded, the data frame cannot be transmitted to the target receiver. Accordingly, a check may be performed to determine whether all frames in queue 208 have been tested to determine whether they can be transmitted in the next consecutive time slot, as shown in block 403. If all frames have not been tested, the next frame in queue 208 may be read and tested, as shown in block 404.

On the other hand, if all queued frames have been tested and there are no frames that can be transmitted in the next consecutive time slot without exceeding the data reception rate capability of its target receiver, then the data transmission for that time slot may be idled, as shown in block 405.

As described above, the frame selector 207 may be implemented with computer-executable instructions that when executed by a processor implement the advantageous features of the present invention. The computer executable instructions may be embodied in a computer usable medium such as a diskette, tape, CD-ROM, RAM, ROM, FPGA (field programmable gate array) or ASIC (application specific integrated circuit).

The foregoing is considered as illustrative only of the application of the principles of the invention. Other arrangements and methods may be implemented by those skilled in the art without departing from the spirit and scope of the present invention.

Claims (11)

1. A method for communicating information to a plurality of receivers having correspondingly different data reception rate capabilities, comprising the steps of:

receiving data frames from an information source to each receiver;

maintaining a queue of the data frames;

identifying a data reception rate capability of a target receiver of the queued data frames;

maintaining a count of frames sent to the target receiver;

comparing the data reception rate capability to the count; based on said comparison, transmitting said queued data frame to said target receiver if said data reception rate capability of said target receiver is not exceeded by transmitting said queued data frame in a next contiguous channel resource slot;

otherwise, the queue is searched for data frames that are transmitted within the next channel resource slot without exceeding the data reception rate capability of its target receiver.

2. The method of claim 1, further comprising:

idling transmission of data frames that can be transmitted within the next consecutive channel resource slot without exceeding the data reception rate capability of its target receiver if no data frames are found in the queue.

3. The method of claim 1, wherein: the data reception rate capability is specified in a header of the frame.

4. The method of claim 1, wherein: the data reception rate capability is specified in a look-up table.

5. A transmitter for use in a communication network, comprising:

a rate controller comprising a data frame buffer and a frame selector, wherein the data frame buffer stores data frames received from an information source of the communication network, the data frames targeted for a plurality of receivers having respective different data reception rate capabilities; and

wherein the frame selector selects a data frame from the buffer for transmission to the target receiver based on a comparison of the count of transmitted frames and a data reception rate capability of the target receiver.

6. The transmitter of claim 5, wherein: the data frame buffer also includes a data frame queue for storing the data frames received from the information source.

7. The transmitter of claim 5, wherein: the data frame buffer is formatted as an array.

8. The transmitter of claim 5, wherein: the data frame buffer is formatted as a linked list.

9. A rate controller for a transmitter, comprising:

a data frame buffer; and

a frame selector;

wherein the data frame buffer stores a data frame received from an information source, the data frame targeted to at least one of a plurality of receivers having different data reception rate capabilities; and

wherein the frame selector selects a data frame from the buffer for transmission to a target receiver based on a comparison of the count of transmitted frames and a data reception rate capability of the target receiver.

10. The rate controller of claim 9, wherein: the data frame buffer also includes a data frame queue.

11. The method of claim 1, wherein the predetermined data reception rate capability is set according to a service agreement.