DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Turning attention now to the drawings, FIG. 1 is a block diagram of a system 100 for providing high speed data service over a wireless connection by seamlessly integrating a digital data protocol such as, for example, Integrated Services Digital Network (ISDN) with a digitally modulated wireless service such as Code Division Multiple Access (CDMA).

[0033] The system 100 comprises two different types of components, including subscriber units 101 - 1 , 101 - 2 , and 101 - 3 (collectively subscribers 101 ) as well as one or more base stations 104 to provide the functions necessary in order to achieve the desired implementation of the invention. The subscriber units 101 provide wireless data and/or voice services and can connect devices such as, for example, laptop computers, portable computers, personal digital assistants (PDAs) or the like through base station 104 to a network 105 which can be a Public Switched Telephone Network (PSTN), a packet switched computer network, or other data network such as the Internet or a private intranet.

[0034] The base station 104 may communicate with the network 105 over any number of different efficient communication protocols such as primary rate ISDN, or other LAPD based protocols such as IS-634 or V5.2, or even TCP/IP if network 105 is an Ethernet network such as the Internet. The subscriber units 101 may be mobile in nature and may travel from one location to another while communicating with the base station 104 .

[0035] FIG. 1 illustrates one base station 104 and three mobile subscriber units 101 by way of example only and for ease of description of the invention. The invention is applicable to systems in which there are typically many more subscriber units communicating with one or more base stations.

[0036] It is also to be understood by those skilled in the art that FIG. 1 may be a standard cellular type communication system such as a CDMA, TDMA, GSM or other system in which the radio channels are assigned to carry between the base stations 104 and subscriber units 101 . This invention, however, applies more particularly to non-voice transmissions, and preferably to digital data transmissions of varying bandwidths. Thus, in a preferred embodiment, FIG. 1 is a CDMA-like system, using code division multiplexing principles for the air interface. However, it is also to be understood that the invention is not limited to using standardized CDMA protocols such as IS-95, or the newer emerging CDMA protocol referred to as IS-95B. The invention is also applicable to other multiple access techniques.

[0037] In order to provide data and voice communications between the subscriber units 101 and base station 104 , wireless transmission of data over a limited number of radio channel resources is provided via forward communication channels 110 - a through 110 - c, and reverse communication channels 111 - a through 111 - c . The invention provides dynamic bandwidth management of these limited channel resources on an as needed basis for each subscriber unit 101 . It should also be understood that data signals travel bidirectionally across the CDMA radio channels 110 and 111 , i.e., data signals originating at the subscriber units 101 are coupled to the network 105 , and data signals received from the network 105 are coupled to the subscriber units 101 .

[0038] FIG. 2 provides an example of how dynamic allocation of radio bandwidth may take place in an example system 100 . First a typical transceiver within a subscriber unit 101 or the base station 104 can be tuned on command to any 1.25 MegaHertz (MHZ) channel within a much larger bandwidth, such as up to 30 MHZ in the case of the radio spectrum allocated to cellular Telephony. This bandwidth is typically made available in the range of from 800 to 900 MHZ in the United States. For PCS type wireless systems, a 5 or 10 MHZ bandwidth is typically allocated in the range from about 1.8 to 2.0 GigaHertz (GHz). In addition, there are typically two matching bands active simultaneously, separated by a guard band, such as 80 MHZ. The two matching bands form a forward and reverse full duplex link between the base station 104 and the subscriber units 101 .

[0039] For example, within the subscriber unit 101 and the base station 170 , transmission processors (i.e., transceivers) are capable of being tuned at any given point in time to a given 1.25 MHZ radio frequency channel. It is generally understood that such 1.25 MHZ radio frequency carrier provides, at best, a total equivalent of about a 500 to 600 kbps maximum data rate transmission speed within acceptable bit error rate limitations.

[0040] In the prior art, it was thus generally understood that in order to support an ISDN type like connection which may contain information at a rate of 128 kbps that, at best, only about (500 kbps/128 kbps) or only three (3) ISDN subscriber units could be supported at best.

[0041] In contrast to this, the present invention subdivides the available approximately 500 to 600 kbps data rate among a relatively large number of channels and then provides a way to determine how to allocate these channels to best transmit data between the base station 104 and each of the subscriber units 101 , and vice versa. In the illustrated example in FIG. 2 , the bandwidth is divided into sixty-four (64) subchannels 300 , each providing an 8 kbps data rate. It should be understood herein that within a CDMA type system, the subchannels 300 are physically implemented by encoding a data transmission with one of a number of different assignable codes. For example, the subchannels 300 may be defined within a single CDMA radio frequency (RF) carrier by using different orthogonal Walsh codes for each defined subchannel 300 . The subchannels 300 are also referred to as “channels” in the following discussion, and the two terms are used interchangeably herein.

[0042] As mentioned above, the channels 300 are allocated only as needed. For example, multiple channels 300 are granted during times when a particular subscriber unit 101 is requesting that large amounts of data be transferred. In this instance and in the preferred embodiment, the single subscriber unit 101 may be granted as many as 20 of these channels in order to allow data rates of up to 160 kbps (20*8 kbps) for this individual subscriber unit 101 . These channels 300 are then released during times when the subscriber unit 101 is relatively lightly loaded. The invention determines the way in which the limited number of channels are divided at any moment in time among the subscriber units 101 .

[0043] Before discussing how the channels 300 are preferably allocated and deallocated, it will help to understand the general architecture of relevant parts of a typical subscriber unit 101 and base station 104 in greater detail. Turning attention now to FIG. 3 , the base station 104 accepts data from incoming data sources 201 through 203 . Each data source 201 through 203 represents any type of data source that is sending data to one or more of the subscriber units 101 . For example, data source 202 may be web server software on network 105 serving web pages to a client web browser operating in conjunction with subscriber unit 101 - 1 , while data source 203 may be an ISDN terminal on network 105 that is sending voice and data to subscriber unit 101 - 3 .

[0044] For each subscriber unit 101 that is in communication with this particular base station 104 , the base station 104 establishes and allocates a respective data buffer 211 through 213 . Data buffers 211 through 213 store the data that is to be transmitted to their respective subscriber units 101 . That is, in a preferred embodiment, there is a separate data buffer in the base station 104 for each respective subscriber unit 101 . As subscriber units enter into and exit out of communication sessions or connections with base station 104 , the number of buffers may change. There is always a one-to-one correspondence between the number of buffers 211 through 213 allocated to the number of subscriber units 101 communicating with base station 104 . The buffers 111 through 213 may be, for example, queues or other memory structures controlled by software, or may be hardware controlled fast cache memory.

[0045] As data is queued up in the buffers 211 through 213 , transmission processor 210 transmits the data from the base station 104 to the respective subscriber units 101 . In the case of forward link transmission (from the base station 104 to the subscriber units 101 ), a selection of a limited number of forward link channels 110 a through 110 c are used. As will be explained, the invention is able to accommodate greater bandwidth for one particular subscriber unit 101 , as more and more data is queued at the base station 104 . That is, as the transmission processor 210 in the base station 104 accepts data from each buffer 211 through 213 for transmission to that buffers' respective subscriber unit 101 , the transmission processor 210 uses only the allocated number of forward link 110 resources assigned to that particular respective subscriber unit. To determine how these channel resources are assigned, the invention provides a channel resource assignor 209 which implements a unique algorithm according to the invention that monitors buffer usage to determine an urgency characteristic of each subscriber unit 101 in order to dynamically assign an optimum number of channel resources to be allocated to each subscriber unit.

[0046] In the reverse direction, each subscriber unit 101 also contains a respective data source 221 through 223 that provides data to data buffers 225 through 227 . The data stored in buffers 225 through 227 is data to be transmitted on one or more of the reverse links 111 a - c back to the base station 104 , for eventual transmission to processes or devices on network 105 that are connected at a network session layer with the subscriber units 101 . Each subscriber unit 101 also contains a transmission processor 231 through 233 for controlling the transmission of data from buffers 225 through 227 back to base station 104 . As in the base station 104 , the transmission processors 231 through 233 only use an allocated number of reverse channel 111 a - c resources assigned to that particular respective subscriber unit 101 .

[0047] In a preferred embodiment of the invention, the channel resource assignor 209 in the base station also monitors the usage of buffers 225 through 227 within subscriber units 101 . This is accomplished via buffer monitors 235 through 237 in each subscriber unit 101 which periodically report buffer characteristics back to base station 104 . The buffer characteristics reports may be piggybacked onto the regular transmission of data on the reverse links 111 a - c.

[0048] Upon receipt of this buffer characteristic information, the channel resource assignor 209 then determines an urgency factor representing the relative need for each subscriber unit 101 to transmit data on the reverse links 111 a - c from their respective buffers 225 through 227 . Using these urgency factors, the channel resource assignor 209 can then dynamically assign an optimum number of channel resources which each subscriber unit may use on the reverse links 111 a - c. This channel assignment information sent back to the subscriber units 101 on the forward links 110 , so that the transmission processors 231 through 233 know their currently allocated channels at all times.

[0049] The channel resource assignor 209 is thus a bandwidth management function that includes the dynamic management of the bandwidth allocated to a particular network layer session connection. Before a further description of the channel assignor 209 is given, it should be first understood that no matter what bandwidth allocation is given to a particular subscriber unit 101 , a network layer communication session will be maintained even though wireless bandwidth initially allocated for transmission is reassigned to other connections when there is no information to transmit. One manner of maintaining network layer communication sessions during periods of reduced allocation of bandwidth for a particular subscriber unit is discussed in detail in the above-referenced U.S. patents, which are assigned to the current assignee of the present invention, and the entire contents of which are hereby incorporated by reference in their entirety.

[0050] In general, bandwidth assignments are made for each network layer session based upon measured short term data rate needs as determined by buffer statistics. One or more channels are then assigned based upon these measurements and other parameters such as amount of data in the buffer, the present resources allocated to a subscriber unit, and probabilities of a requirement of a subscriber unit to transmit data or priority of service as assigned by the service provider. In addition, when a given session is idle, a connection is preferably still maintained end to end, although with a minimum number of channel resources allocated, such as a single subchannel being assigned. This single subchannel may eventually be dropped after a predetermined minimum idle time is observed.

[0051] FIG. 4 illustrates a buffer 360 in detail. Buffer 360 can be any one of the buffers 211 through 213 or 225 through 227 in either the subscriber units 101 or base station 104 . The buffer 360 accepts data 365 and stores this data while awaiting transmission on forward links 110 from the base station 104 to a respective subscriber unit 101 , or on reverse links 111 from one of the subscriber units to the base station 104 . Each buffer has associated with it L thresholds, which in this example are labeled 1, 2, . . . L and numbered 361 , 362 and 363 respectively. These L thresholds are an indication of how much data is currently stored in the buffer 360 . That is, the thresholds are “characteristics” in the sense that they provide an indication of how much buffer memory is currently in use.

[0052] As data 365 enters and fills buffer 360 , until transmission of this data takes place, the data may fill buffer 360 so much so as to cross certain of the thresholds 361 through 363 . For instance, in FIG. 4 , data blocks 365 - a through 365 - d have just filled buffer 360 enough to approach the first threshold 361 . The last block of data 365 - n exists between thresholds 361 and 362 and so the buffer 360 has stored data in an amount exceeding the first threshold 361 . In other words, buffer 360 as shown has a threshold level of “1”, corresponding to the first threshold 361 .

[0053] As explained above, the channel resource assignor 209 in base station 104 obtains an indication of the threshold level for each buffer 225 through 227 in each respective subscriber unit 101 - 1 through 101 - 3 . By determining how much data is in each buffer, the resulting data arrival rates of data to each buffer, and the resources currently allocated to transmit data from a buffer, an urgency factor for each data source attempting to transmit on the reverse links 111 is computed. A similar computation takes place for each data transmitter on the forward links 110 .

[0054] More particularly, an urgency factor is calculated for each buffer based on these buffer characteristics, that indicates the relative need to empty the buffer for that particular receiver as compared to the buffers in other receivers. Given urgency factors for each buffer having data queued for transmission to a waiting receiver, the invention is able to determine how to allocate the available channels to best transmit this data.

[0055] The urgency factor for buffer 360 , for example, is based on statistical information gathered for the accumulation of data 365 . The statistical information is used to compute probabilities of when data 365 exceeds or does not exceed certain of the L discrete data thresholds 361 , 362 and 363 . Thus, as data 365 enters buffer 360 and exceeds the first threshold 361 , the urgency factor for that buffer, and hence for the receiver associated with that buffer (i.e., for example, one of the subscriber units 101 for which data 365 in buffer 360 is destined) increases.

[0056] The urgency factor for buffer 360 is also based upon conditional probabilities of how much time has passed since buffer 360 has had data 365 transmitted from the buffer to its intended receiver, as well as how much time has passed since data 365 has been received at the buffer 360 for storage until transmission may occur. The urgency factor depends partly on the history of the time that the data level in the buffer exists between each threshold in the buffer and on the number of times each threshold, including the maximum buffer capacity, is exceeded.

[0057] The urgency factor is also based on how close data 365 is to the last threshold L 363 , which indicates that the buffer is reaching maximum capacity. The urgency factor therefore also accounts for the probability of exceeding the capacity of buffer 360 , based on exceeding the maximum threshold L 363 .

[0058] The channel resource allocator 209 therefore calculates an urgency factor, U, for each of M buffers, where M is the total number of buffers used in the reverse 111 and forward 110 links. The urgency factor for the buffers servicing the forward links 110 are calculated independently of urgency factors for the other buffers servicing the reverse links 111 , and the buffers servicing each transmission direction of a particular connection between a particular one of the subscriber units 101 and the base station 104 are independent of one another.

[0059] At any given time, a given buffer J has a number of channels, N _J , which is the number of channels already allocated to that particular buffer J. Accordingly, N _J must range from 1<N _J <N _MAX , where N _MAX is the maximum number of channel resources 300 that may be assigned to any one particular buffer, and hence to any one link. In the preferred embodiment, N _MAX can be as high as 20 channels, with each channel operating at approximately 8.55 kilobits per second (kbps) or at 13.3 kbps, depending upon a rate selection as determined by which CDMA standard is used. Thus, if a particular buffer is assigned the maximum number of channels to accommodate data transfers for high bandwidth applications, instantaneous data rates may be achieved as high as from about 171 kbps to 260 kbps.

[0060] The urgency factor U for a given buffer is equal to the sum of weighted conditional probabilities. Each conditional probability represents the chance of exceeding the last threshold L, within a time frame, T _S given that the data in the buffer has already exceeded a particular threshold E _i . The time frame T _S corresponds to the maximum time needed to reallocate a resource. The probabilities for an urgency factor U for a single buffer are all computed in a similar manner, but are based upon different thresholds within that buffer. Thus, as the probabilities for each threshold change with the various demands for service, the urgency factor for that particular buffer also changes. The computed urgency factor for each buffer may also be based upon a quality of service of the communication sessions, wherein the quality of service is based upon at least one of throughput, data rate, latency and jitter, for example.

[0061] In a preferred embodiment, the probability of exceeding a particular threshold E _L in time T _S given that another threshold E _i is exceeded is given by: 1 $P_{\mathrm{EL}}\left(T_S|E_i\right)=\frac{P_{\mathrm{EL}}\left(E_i\right)·P_{\mathrm{EL}}\left(T_S\right)}{P_{\mathrm{EL}}\left(E_i\right)}$

[0062] Threshold E _i is used in the above equation when computing the probability of exceeding a threshold E _L , in a time period T _S , given that the data level in the buffer has already crossed threshold E _j . Since this is an indirect computation, it may be derived from the formula: 2 $\frac{\sum (P_{\mathrm{EL}}\mathrm{within}T_S\mathrm{of}E_i/\sum \left(E_i\mathrm{for}T_S\right)}{P_{\mathrm{EL}}\left(E_j\right)}$

[0063] The probabilities that make up the urgency factor U for a particular buffer are also weighted before they are summed, such as

U=Σ _i P _EL ( T _S |E _i )· W _i ( N )

[0064] The weight W _i (N) for each probability is selected to optimize the resource allocation. For example, the weight is selected based upon which threshold is crossed and therefore effects the urgency factor for that buffer by increasing the weight of the summed probabilities used to compute that urgency factor for that buffer.

[0065] Once an urgency factor U for each buffer has been computed, the channel resource assignor 209 determines how to allocate the available channels among the buffers. This is accomplished in a preferred embodiment by determining which buffer has the highest urgency factor and which one has the lowest. Next, the highest and lowest urgency factors must exceed respective high and low urgency thresholds. If this is true, one resource channel is deallocated from the buffer with the lowest urgency factor and is reallocated to the buffer with the highest urgency factor. In this manner, the channel resources for buffers may change over time based upon the urgency factors of the buffers.

[0066] Also, when N _J is 1, there is only one channel allocated to a particular buffer. In this state, the assigned channel resource may be reallocated (i.e., taken away) to another buffer if there is no data in buffer and if the probability of exceeding the buffer capacity within the time it takes to reassign this initial resource, P _E ^L (T _S |E _O ), is less than the probability of reaching the buffer overflow limit P(E _L ), which is a predetermined constant.

[0067] While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described specifically herein. Such equivalents are intended to be encompassed in the scope of the claims.