GB2359700A

GB2359700A - Communication system, packet scheduler and operating method therefor

Info

Publication number: GB2359700A
Application number: GB0004555A
Authority: GB
Inventors: Eric Villier; Stephen Barrett; Luis Lopes
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 2000-02-25
Filing date: 2000-02-25
Publication date: 2001-08-29
Also published as: GB0004555D0

Abstract

A cellular communication system (10), as shown in FIG.1, contains a wideband communication resource utilised to support traffic, including data packets (69), between subscriber units (32-44) and base station equipment (12-20) arranged to administer system access on a cell-by-cell basis. A packet scheduler (70) within infrastructure of the communication system (10) is operationally responsive to a determined level of uplink loading of the wideband communication resource (68) and acts to assess and then selectively notify an availability of data packet resources supported by the wideband communication resource (68) to subscriber units requiring data packet transmissions (69).

Description

2359700 CE30809P-Villier COMMUNICATION SYSTEM, PACKET SCHEDULER AND

OPERATING METHOD THEREFOR

Field of the Invention

This invention relates, in general, to a packet scheduler and an operating methodology supporting packet data transmissions and is particularly, but not exclusively, applicable to a packet scheduler for a cellular communication system, such as a wireless code division multiple access (CDMA) system.

Background of the Invention

In cellular communication systems, user equipment (such as mobile stations and remote terminals) communicate with base stations over dedicated uplink and downlink communication resources. Since wireless communication is particularly susceptible to interference, both up-link and down-link transmissions within a particular cell are generally subject to power control in order to provide an - interference-limited environment. Inevitably, however, cell boundaries in a radio- environment are non-discrete in view of propagation varying according to the instantaneous physical environment and so overlap does occur between adjacent (or neighbouring) cells that form the coverage area of the system.

Generally, as user equipment (LIE) moves from the coverage area of one cell to the coverage area of another cell, a communication link will change from being between the UE and a first base station of the first cell to being between the UE and a second base station of the second cell; this is known as a handover.

For completeness, it should be noted that, within the specification, the term "UE" is used interchangeably with the term "subscriber unif' or the like.

' Certain communication systems, such as CDMA, advocate use of softhandover algorithms in which up-link communications from a subscriber unit within a specific cell are decoded by multiple base stations sub- systems (BSSs) in adjacent (i.e. non-primary) cells. As will be understood, such soft-handover CE30809P-Villier provides space diversity and consequently a better quality of service (QoS) for a nominally selected transmitted power level. Consequently, in systems that constantly seek to limit an interference environment, soft- handover can provide an improved QoS (e.g. reduced frame erasure rates (FERs) or reduced bit error 5 rates (BERs) for the same power.

Base stations within a cellular systems are interconnected by a fixed network comprising communication fines, switches, interfaces to other communication networks and various controllers required for operating the network. A call from a UE is routed through the fixed network to the destination specific for the call. If the call is between two UEs of the same communication system, the call is typically routed through the fixed network to the base station of the cell in which the other remote terminal currently resides, although in special instances local routing of a call through a common base station obviates network overhead associated with network transcoding functions. A connection is thus established between a calling party and a called party through, for example, two serving base stations and the fixed network. Clearly, if the call is' between a remote terminal and a telephone connected to a Public Switched Telephone Network (PSTN), then the call is routed via the serving base station and an interface between the public land mobile network (PLMN, i.e. the cellular system) and the PSTN.

The demands for system access have, in fact, resulted in the development of overlaid cellular systems in which a remote terminal may be serviced by a base station in a particular system layer, which system layer is selected dependent upon operational (e.g. loading) parameters within the cell andlor physical characteristics attributable to a mobile station. In this instance, handover may therefore simply occur between system layers, with certain base stations of underlaid cells (such as pico-cells and micro- cells) being potentially collocated with base stations of the macro-cell. Furthermore, with limited radio frequency spectrum available for use in the cellular communication systems, there is a CE30809P-Villier necessity simultaneously to re-use or otherwise share spectrum between all subscriber units affiliated with system providers, and this has therefore spawned a number of different communication protocols such as CDMA, time division multiplexing (TDM) and the like.

As previously indicated, one method of sharing spectrum is by the technique known as Code Division Multiple Access (CDMA). More especially, in a Direct Sequence CDMA (DS-CDIVIA) communication system, prior to transmission, information signals are multiplied by a high rate spreading code such that the information is spread over a larger frequency spectrum. In other words, a narrowband signal is spread and transmitted as a wideband signal. Spreading codes are chosen to minimise the interference caused between remote terminals typically by choosing orthogonal codes when possible.

At an addressed receiver unit, the original narrowband signal is regenerated by - multiplication of the received signal with the same code, whereas signals spread -- using of a different code will be ignored and will remain as a coded wideband signal. As will be understood, the majority of interference caused by interfering signals received in the same frequency spectrum as the wanted signal can therefore be removed in a receiver by filtering (and use of the spreading code), thereby allowing a plurality of remote terminals to be accommodated in the same wideband.

A further description of CDMA communication systems can be found in "Spread 25 Spectrum CDMA Systems for Wireless Communications", Glisic & Vucetic, Artech House Publishers, 1997, ISBN 0-89006-858-5. Examples of CDMA cellular communication systems are IS 95 standardised in North America and the Universal Mobile Telecommunication System (U1VITS) currently under standardisation in Europe.

CE30809P-Villier Traditional traffic in mobile cellular communication systems has been circuit switched voice data where a permanent link is set up between the communicating parties. In the future it is envisaged that data communication will increase substantially and typically the requirements for user equipment to transmit data will not be continuous but will be at irregular intervals (in view of the inherent bursty nature of data). Consequently, it is inefficient to have a continuous dedicated link established between users and instead a significant increase in packet- based data traffic is expected, where the transmitting remote terminal seeks to transmit the data in discrete data packets when necessary. An example of a packet based system is the General Packet Radio Service (GPRS) system introduced to the Global System for Mobile communication (GSM). Further details on data packet systems can be found in "Understanding data communications: from fundamentals to networking, 2 1d ed.", John Wiley publishers, author Gilbert Held, 1997, ISBN 0-471-96820-X In packet-based systems where a high number of subscribers requir6 resources for packet transmissions at unknown and irregular intervals, it is important to optimise utilisation of limited communication resources and hence there has been a desire to schedule the order and time for transmission of the individual packets. This becomes even more important when different data packets have different requirements with respect to bandwidth, delay, bit error rate/QoS, etc. Therefore, most packet-based systems contain schedulers that control when the -individual data packets are transmitted and therefore share the available resource, whether this be time-slots in a time division multiple access (TDMA) system or power and codes in a CDMA system. Known schedulers have, to date, been optimised for environments other than CDMA systems. For example, scheduling algorithms used for GPIRS are optimised for a Time Division Multiple Access (TDMA) system and such GPRS scheduling algorithms are therefore not optimal for CDMA systems where codes and power must be shared.

CE30809P-Villier A scheduler is typically implemented as a software program running on a suitable processor such as a microprocessor or a digital signal processor within a node or a radio network controller (in the sense of U1VITS and CDMA).or a base station, BSS or base site controller (in the sense of GSM). The location of the schedule is, in fact, arbitrary, Indeed, a scheduler could in principle be situated anywhere in the communication system or can be distributed over a plurality of components in the network.

An introduction to schedulers can be found in "Service discipline for guaranteed performance service in packet-switching networks", Hui Zhang, Proceedings of the IEEE, volume 83, no. 10, October 1995.

In CDMA, it will be appreciated that the total data throughput is limited by the interference at the receiver caused by transmissions to other users. Moreover, since a single cell re-use of carrier frequency is employed, interference may originate from connections within the same cell (intra-cell interferendo) or from adjacent cells (inter-cell interference). A successful sharing of the available power in a cell requires an accurate knowledge of these interference levels so that the signal-to-noise (SIN) ratio for each connection is appropriate for a desired blocking error rate (as determined by the FER). In order to perform an optimal spectral and communication resource allocation, it may be necessary to take into account subscriber unit activity in all other cells of the communication system.

It has been proposed to implement a scheduler on a cell-cluster basis (rather than having a single, system-wide scheduler for an entire network). This system configuration potentially reduces control overhead (i.e. load) on leased communication links (such as E1 and T1 links) between the scheduler and the respective base stations, whilst also reducing complexity of the scheduler and potentially obviating the need to co-ordinate all system-wide scheduling on a CE30809PLO1fler simultaneously basis. The size of such clusters is arbitrary, and generally depends on the acceptable complexity of the scheduler.

In a frame-based communication system, such as U1VITS, communication is 5 divided into discrete time intervals or frames and the communication resource is allocated in granularity of a single frame. In UMTS, packets of information to be transmitted in one time frame are generally scheduled and in a previous time frame. For example, in relation to the up-link, a subscriber unit (i.e. the UE) will transmit a resource request to the fixed network infrastructure, which resource request will typically include a size of queued packets together with Quality of Service related information, e.g., time of arrival, priority, BER. This resource request is then communicated to the scheduler.

In the UMTS specification [release 1999], a procedure called dynamic resource allocation control (DRAC) has been introduced as a way of regulating data transmissions from subscriber units (i.e. UEs). Within DRAC (which is an uplink associated function), an assigned base station servicing a-subscriber unit in a cell measures uplink transmissions in order to compute an overall traffic loading for the up-link. In response to the assessed level of loading, which is may be a system-wide loading determined having regard to RNCs but in any event is consequential on the desired interference-limited environment of a wideband CIDIVIA system, the assigned base station broadcasts on a forward access.channel (FACH) both an estimated transmission probability for UE accessibility to the up-link and an indication of a maximum bit rate (i.e. load) that can be accommodated in the uplink channel. As will be understood, the FACH is a common channel and is therefore assessable to all UEs receptive to and able to decode the FACH. Essentially, the transmission probability provides an indication of the ability of a particular cell to handle/support uplink transmissions, whereas the maximum bit rate (which varies with loading) indicates, as its name suggests, the maximum allowable uplink transmission rate for a subscriber unit.

CE30809P-Villier In response to receipt of the FACH, the subscriber unit makes/generates a pseudo-random probability which is generally higher than or lower than the received transmission probability. Of course, the pseudo-random probability could be identical to the received transmission probability in which case an arbitrary but predetermined decision is taken as to whether the psoudo-randorn probability is taken to be higher or lower. In the event that the pseudo-random probability is higher than the received transmission probability then the subscriber unit is authorised to access the base station and establish a call to the maximum allowed data rate. Conversely, if the pseudo-randorn probability is lower than the received transmission probability then the subscriber unit is blocked and must attempt system access later. In this way, DRAC controls (on average) the number of users accessing a dedicated channel (DCH) at the same time. DRAC also therefore controls the bit-rate at which transmissions take place.

In other words, based on some uplink load measurements done by -each base station, the RNC (radio network controller) determines for the users, in each cell, a probability of transmission and a maximum bit rate. These two parameters are then communicated to the users on the FACH, and each subscriber unit then decides, in a statistical way analogous to tossing a coin, whether or not the subscriber unit can transmit and at what rate transmission can occur.

1t will be appreciated that DRAC is applicable to the regulation of uplink data packet transmissions but is generally inapplicable to voice transmission because delay in voice calls is disruptive of coherent communication and is hence at least undesirable and usually unacceptable.

Should blockinglcontention arise within uplink data packet transmissions (identified by an inability of the BSS to accurately decode uplink data packets), then DRAC causes a re-estimation of the transmission probability and bitrate and, thereafter, broadcast of this new transmission probability and bit-rate in an CE30809P-Villier up-dated FACH. Clearly, with data packet loss, the system generally operates either to request the re-transmission of the lost data at a later point time or disregards such corrupted data packets and marks an information accordingly.

From an infrastructure perspective, DRAC is relatively simple to support, whereas DRAC places relatively processing demands on the UE. More especially, a significant proportion of the UE complexity arises from the fact that the UE has to decode both a DCH and a FACH. Indeed, the UE must necessary include additional processing capabilities and increased memory to support DRAC and so there is an associated increase in manufacturing costs (which may be passed on to the subscriber). Furthermore, with soft-handover, UEs should decode the FACHs of at least the cells in its active set, or even more likely the FACHs of all its neighbour cells. Unfortunately, with the potential (and generally desirable) requirement to listen to FACHs of adjacent cells to ensure that power transmissions from a subscriber supporting data packet - transmissions are cut to avoid inter-cell interference, there is a corresponding- power budget issue for FACH transmissions across the system. Consequently, implementation of DRAC in its present form potentially provides for an overall increase in a system's interference environment (which is clearly contrary to desired aims of interference limitation in CDMA-type systems). Putting this in a slightly different context, optimal DRAC operation requires the UE to use packet transmission parameters corresponding to a worst-case scenario (lowest -product transmission probability times maximum bit rate) for its local (multi-cell) environment.

As will be understood, the DCH is an in-call, subscriber-specific channel that supports the transmission of control information/data from the radio resource manager (RRM) of the base station sub-system to the subscriber unit. For example, the DCH is used to control subscriber unit power (which is essential in the interference-limited environment of a wideband CDMA-type system).

CE30809P-Villier ii) It will be appreciated that, in the context of packet data transmissions in a wideband system, DRAC is desirable to regulate the number of subscribers accessing DCHs at the same time, but DRAC is presently deficient in that it:

i) potentially increases an overall inter-cell interference level; requires a UE to be manufactured to support the DRAC operating methodology (which requires increased complexity and costs); iii) a system operator cannot really rely upon the benefit of DRAC since it is left open to a subscriber unit manufacturer as to whether they include the necessary functionality and hardware to support DRAC within their subscriber units; and iv) is a subscriber probabilistic approach that is potentially subject to blocking and which operates on an access basis to a lowest assessed transmission probability from a local cluster of cells.

Summa!y of the Invention According to a first aspect of the present invention there is provided a packet scheduler for a wideband cellular communication system containing at least one cell supporting a plurality of subscriber units requiring access to a wideband communication resource that selectively supports uplink data packet transmissions from at least some of the plurality of subscriber units, the packet scheduler responsive to means for determining a level of uplink loading of the wideband communication resource, the packet scheduler comprising: means, responsive to the level of uplink loading, for assessing an availability of data packet resources supported by the wideband communication resource; and means for causing selective notification of the availability of data packet resources to subscriber units requiring data packet transmissions.

The means for assessing the availability of data packet resources is preferably operational responsive to an interference environment of at least a primary cell serving a subscriber unit arranged to support data packet transmissions. In one embodiment, the means for assessing the availability of data packet resources CE30809P-Villier is operational responsive to a perceived level of signal propagation loss from cells other than a primary cell serving a subscriber unit arranged to support data packet transmissions. In another embodiment, the means for causing selective notification of the availability of data packet resources is arranged to utilise a dedicated control channel to communicate the selective notification.. In a further embodiment, the means for determining the level of uplink loading is arranged to monitor a plurality of cells and the means for assessing the availability of data packet resources is operational responsive to a highest traffic loading within the plurality of cells. The parameter by which up-link load.ng is assessed can, of course, be dependent upon a combination of several criteria.

Preferably, the means for causing selective notification of the availability of data packet resources is arranged to utilise a transport format combination JFC) message of a dedicated control channel to communicate the selective notification.

In a second aspect of the present invention there is provided a wideband cellular communication system containing; at least one cell providing a radio coverage area a plurality of subscriber units located within the radio coverage area, the plurality of subscriber units serviceable by a wideband communication resource selectively supporting uplink data packet transmissions from at least some of the plurality of subscriber units; means for determining a level of upiink loading of the wideband communication resource; and packet scheduling control logic responsive to the means for determining a level of uplink loading of the wideband communication resource, the packet scheduling control having: means for assessing an availability of data packet resources supported by the wideband communication resource; and means for causing selective notification of the availability of data packet resources to subscriber units requiring data packet transmissions.

CE30809P-Villier In a further aspect of the present invention there is provided a method of scheduling up-link data packet transmissions on a wideband communication resource from subscriber units of a wideband cellular communication system containing at least one cell) in which the subscriber units are located and wherein at least some of the plurality of subscriber units selectively require access to the wideband communication resource, the method comprising: determining a level of uplink loading of the wideband communication resource: assessing, in responsive to the level of uplink loading, an availability of data packet resources supported on the wideband communication resource; and causing selective notification of the availability of data packet resources to subscriber units requiring data packet transmissions.

In another aspect of the present invention there is provided a computer program product for a data packet scheduling function operational on a scheduling controller for a wideband cellular communication system containing at least one - cell) in which subscriber units are located, and wherein at least some of the subscriber units selectively require access to the wideband communication resource to support data packet transmissions, the computer program product comprising: code that directs the scheduling controller to be responsive to a determination of a level of uplink loading on the wideband communication resource; code that directs the scheduling controller to assess, in responsive to the level of uplink loading, an availability of data packet resources supported on the wideband communication resource; and code that directs the scheduling controller to cause selective notification of the availability of data packet resources to subscriber units requiring data packet transmissions; wherein the codes reside in a computer readable medium.

Advantageously, the present invention provides a statistical mechanism of regulating packet transmissions within a wireless CDMA network or the like, which statistical mechanism is operationally supported within infrastructure (as opposed to subscriber) equipment. Consequently, the present invention requires CE30609P-Villier ro change to the UMTS (or equivalent) air-interface standard and can be implemented using a relatively simplistic proprietary algorithm within, for example, a radio network controller or the like. Significantly, the present invention beneficially allows migration of an existing data packet subscriber base into enhanced communication system architectures since all user equipment can benefit immediately from data packet scheduling at an infrastructure node. In other words, unlike existing DRAC scheduling proposals, there is no requirement for any modification of subscriber units (UEs) functionality or processing capabilities (which directly impacts battery life). Moreover, the present invention releases the UE from having to look to specific FACH messages and, in fact, frees-up FACH resources for purposes other than data packet scheduling thereby improving system efficiency and operation. In addition, the present invention allows soft handover to be exploited directly by the RNC (or the like) to decide on the maximum bit rate for a packet transfer, which bit rate can be adjusted dynamically.

Brief Description of the Drawings

An exemplary embodiment of the present invention is described below, by way of example only, with reference to the Drawings, in which:

FIG. 1 is an illustration of a conventional cellular communication system, such as a wideband CDMA-type system, that is adapted to support packet scheduling principals of the present invention; FIG. 2 illustrates a flow chart of a method of scheduling packets in accordance with a preferred embodiment of the present invention.

Detailed Description of a Preferred Embodiment

There are many ways of dealing with packet data transmissions in a wireless network. These packet data transmission methods fall into three principal categories, namely: i) assignment of a dedicated circuit for packet data 30 transmissions; ii) regulation of packet data transmissions in a statistical way; and iii) scheduling of packet data transmissions in a deterministic way. These three CE30809P-Villier possibilities have, in fact, been ordered from a technique that is relatively simple to implement to one that is the most complex. Moreover, the ordering above is also reflective of attainable system performance with the poorest performance being attained from assignment of a dedicated circuit and the most efficient from 5 scheduling packet data transmissions in a deterministic way.

The present invention has realised that conventional approaches for scheduling of data packets can be improved in a CDMA-type system environment by considering parameters specific to CDMA..fhen scheduling. The present invention focuses on uplink data packet transmissions of a W-CDMA system in which the resource to be managed (i.e. that is to be shared amongst all users) is the level of interference produced by each user across the network. Consequently, code limitation is not an issue in then present invention. The disclosure proposes a hybrid scheme failing between the second and third categories of packet data transmission methodologies identified above, whereby the network of the present invention both admits more packet users than it would if they were circuit-switched users (and hence improves the total system throughput) and manages statistically the wideband radio resource to control access to channel resources of subscribers admitted to the system.

Turning briefly to FIG. 1, there is shown a conventional cellular communication system 10, such as a wideband CDMA-type system of a UMTS environment, lhat is adapted to support packet scheduling principals of the present invention.

The communication system 10 contains a plurality of base stations 12-20 each covering a geographical area that defines a cell 22-30. A multiplicity of remote subscriber units 32-44 are associated with the communication system and communicate with each other or to other systems 46-50 via the base stations 12-20. In this context, base stations should be construed broadly to include base transceiver equipment 52 and resource managers 54, as exemplified in cell 26.

The resource manager 52, as will be appreciated, administers control of calls CE30809P-WIlier within its cells by setting, for example, power levels and other control parameters readily appreciated by a skilled addressee.

Typically, some of the base stations 12-14 are connected to a first common controller 56, known as a Node B in UMTS, via communication links 58-60 (which may be optical fibre or wireline links). Other base stations 16-20 are connected to other Node B controllers 62. The Node B controllers 56, 60 within the system are connected together through a Radio Network Controller (RNC) 64 that provides gatp.ways to other communication systems via a wide area network or asynchronous transmission mode (broadband) network 66. The communication systems 46-50 that are accessible to the subscriber units 32-44 may be fixed public switched telephone networks 46, web servers 50 and network peripherals 48 or the like. Such communication systems 46-50 may communicate with at least some of the subscriber units 32-44 through a packet data transmission scheme, e.g. using the internet protocol.

The subscriber units 32-44 (which may, for example, be mobile units or fixed data terminals) each have independent communication needs and typically therefore request access to different services at different times. As such, at any particular time, some of the subscriber units 3244 may be idle within a cell whereas others may be active andlor undergoing handover or s^handover. The resource requirement for eachindividual subscriber units 32-44 may vary significantly over time so that a remote terminal 32-44 may sometimes require no transmissions and at other times require long transmissions at high data rate.

The resource requirement for each subscriber unit 32-44 from the communication system can thus vary significantly, and in order to ensure that the available resource is used optimally an efficient scheduling of packets from the different remote terminals is supported by the communication system 10 in accordance with the present invention. Some of the subscriber units 32-44 may, of course, communicate through use of circuit switched connections.

CE30809P-Villier A wideband communication resource 68 is separated into individual channel resources using spreading codes. The individual channel resources typcailly support voice calls and data in the form of packets 69 in full- duplex (or simplex) operating modes. Separate wideband channel resources may be'provided for the uplink and downlink, if spectral allocation permits or if desired.

The scheduling task is preferably performed by a scheduler 70 shown as being associated with the RNC 64. Of course, scheduler functionality could be distributed through the infrastructure of the communication system 10. The scheduler 70 effectively includes a processor 72 and associated memory 74 configured to assess uplink loading and bandwidth for packet transmissions on a cell-by-cell and system wide basis, in accordance with conventional techniques known to the skilled addressee. Such measurement techniques for assessment of up-link loading include measuring the total received power or measuring the power received in individual channels (codes).

According to the underlying inventive concept of the present invention, DRAC control of subscriber access to packet data resources is integrated into an infrastructure-based function that allows data packet access control on an individual basis to selected individual subscriber units having regard to a system interference environment. Consequently, the present invention leads to optimised data packet resource utilisation within the communication system. Essentially, according to the present invention, the access control of DRAC is removed from the subscriber unit with the decision on data packet access left to an infrastructure scheduler function that assimilates both system and cell uplink loading to identify a useable uplink capacity that can be exploited by a selected subscriber unit within a particular cell.

In more detail, the scheduler of the preferred embodiment of the present invention operates to determine a level of uplink loading (potentially in a similar CE30809P-Villier way to the mechanism suggested currently in DRAC) and then, instead of having the BSS (or the like) communicate the transmission probability and maximum bit rate to a UE requesting packet data service, the scheduler transmits a packet data instruction detailing available bandwidth to the UE through a transport format combination JFC) control message As will be understood, the TFC control message is a layer-3 message sent on UE to an assigned downlink DCH.

By having the decision making process of access to data packets resources resolved by the RNC (or the like) within the infrastructure, the present invention can also address propagation loss issues prevalent within the existing DRAC solution. Specifically, as will be understood, DRAC is presently configured to take into account the most heavily loaded uplink cell, with the UE selecting its decision-making threshold in response to receiving FACH data from this distant cell; this is particularly the base in soft-handover operation. In contrast, since the - system of the present invention is aware of the distribution of cells within the system as a whole, the scheduler of the present invention can take into account anticipated path propagation loss between cells and hence can potentially assign higher powerlincreased packet data rates in situations where the scheduler considers the distant cell to be a negligible interferer with respect to a primary cell serving a UE requiring access to data packet resources. The scheduler of the preferred embodiment of the present invention is therefore -more responsive to uplink loading than prior art systems, and is able to take account of greater amounts of loading information to arrive at an optimum solution for selected subscriber access to data packet resources.

Briefly referring to the flow diagram of FIG. 2, a preferred operating methodology 100 is shown. In essence, the system of the present invention continuously determines 102 a level of up-link loading of a wideband communication resource. In response to the determined level of up-link loading, an assessment 104 of an availability of data packet resources is made. At some point in the CE30809PLViffier flow, the system determines whether a data call has been initiated 106, with a negative response 108 looping the system through steps 102 to 106. With initiation of a data call 110, the system notifies 112 availability of data packet resources in a VC message of DCH. Generally, one can expect that the flow will involve a determination 114 as to whether the data call is ongoing 116 or whether the call is terminated 118 (at which point the flow ends and the process returns to its beginning). If the data call continues 116, then a determination 120 is made of the level of up-link loading of the wideband communication resource. Following the determination of 120, the system again assesses 122 an availability of data packet resources and notifies 124 the in-call subscriber unit of the availability of data packet resources using a TFC message in the DCH.

The present invention considerably simplifies control transmissions and, in fact, eliminates DRAC-associated FACH transmissions. In other words, the present invention releases the UE from having to look to specific FACH messages and, - in fact, frees-up FACH resources for purposes other than data packet- scheduling, thereby improving system efficiency and operation. In addition, the present invention allows soft handover to be exploited directly by the RNC (or the like) to decide on the maximum bit rate for a packet transfer, which bit rate can be adjusted dynamically. Altematively, rather than having the BSS respond to a data packet resource request from a specific UE, the BSS can operate in an independent mode whereby there is no UE prompt for data packet access -scheduling. In this latter (and preferred instance), the BSS continuously monitors uplink loading and informs UEs in a timely fashion of their abilities to access data packet resources through the TFC control message in the DCH associated with a call. Clearly, if the subscriber unit is idle, then no DCH resources are assigned and the mobile, by default, does not require access to data packet resources.

The preferred embodiment of the present invention therefore eliminates the need for modification of UEs to support DRAC-type solutions, and generally CE30809P-Villier allows all UEs in the communication system to benefit from optimised access to data packet resources. Indeed, UE complexity otherwise previously necessary to support DRAC is obviated and specific DRAC- related FACH transmissions are eliminated from the system of the present invention. Furthermore, soft handover can be exploited directly by the RNC of the preferred embodiment to decide on the maximum bit rate, thereby allowing the system of the present invention to benefit from an overall reduction in interference and an improvement in QoS.

It will, of course, be appreciated that the above description has been given by way of example only and that modifications in detail may be made within the scope of the present invention. For example, whilst the foregoing description focuses on an embodiment compliant with the current approach for the standardisation of UMTS, it will be apparent that the invention is not limited to this application and can be applied to CDMA-type systems and other communication systems demanding support of data packet transmissions. While the present invention is applicable to a multiple cell system, the issue of wideband (coded) access to data packet resources is relevant to a single cell environment and so the present invention finds application in single and multiple cell scenarios. Furthermore, the present invention, although described in relation to a multi-cell environment, could be employed within a single (potentially low power) cell, such as envisaged within a household, where multiple data -appliances vie for allocation to data packet resources from a wideband communication resource.

With the packet data scheduler of a preferred embodiment realisable as a software function, it is contemplated that such software can be provided to an existing RNC, Node B or the like in the form of a computer program product, such as on a CD-ROM or digital versatile disk (DVD). Consequently, migration of an existing communication system to an enhanced system able to support readily data packet transmissions is easily accomplished. Moreover, with the CE30809P-Villier RNC, Node B or the like potentially containing control intelligence sufficient to support scheduler code according to a preferred embodiment of the present invention, such code could also be supplied to the intelligence for storage in its associated memory by software upgrade through a network download of suitably encoded signals, such as a java applets. Clearly, the form by which subscribers are notified by the scheduler of the availability of data packet resources is arbitrary, with the use of the TFC message one mechanism that is relatively simple to implement. Consequently, notification using a TFC message of the DCH should be considered to be exemplary and not limiting.

In the context of the present invention it will be understood that the scheduler function is a probabilistic function rather than a deterministic function, albeit that its label is indicative of the outcome that is achieved by the system of the present invention. Consequently, the term "scheduler" (and its equivalents) should be construed loosely and taken in the context in which the present invention is framed.

CE30809P-Villier

Claims

1. A packet scheduler for a wideband cellular communication system containing at least one cell supporting a plurality of subscriber units requiring access to a wideband communication resource that selectively supports uplink data packet transmissions from at least some of the plurality of subscriber units, the packet scheduler responsive to means for determining a level of uplink loading of the wideband communication resource, the packet scheduler comprising: means, responsive to the level of uplink loading, for assessing an availability of data packet resources supported by the wideband communication resource; and means for causing selective notification of the availability of data packet resources to subscriber units requiring data packet transmissions.

2. The packet scheduler according to claim 1, wherein the means for assessing the availability of data packet resources is operational responsive to an interference environment of at least a primary cell serving a subscriber unit arranged to support data packet transmissions.

3. The packet scheduler according to claim 1 or 2, wherein the means for assessing the availability of data packet resources is operational responsive to a perceived level of signal propagation loss from cells other than a primary cell serving a subscriber unit arranged to support data packet transmissions.

4. The packet scheduler according to claim 1, 2 or 3, wherein the means for causing selective notification of the availability of data packet resources is arranged to utilise a dedicated control channel to communicate the selective notification.

5. The packet scheduler according to claim 4, wherein the means for causing selective notification of the availability of data packet resources is CE30809P-Villier arranged to utilise a transport format combination (TFC) message of a dedicated control channel to communicate the selective notification.

6. The packet scheduler according to any preceding claim, wherein the means for determining the level of uplink loading is arranged t o monitor a plurality of cells and the means for assessing the availability of data packet resources is operational responsive to a highest traffic loading within the plurality of cells.

7. The packet scheduler according to any preceding claim, wherein the packet scheduler is coupled to at least one of a radio network controller and a base station sub-system.

8. The packet scheduler according to any preceding claim, wherein the wideband cellular communication system supports a code division multiple access protocol.

9. A wideband cellular communication system containing:

at least one cell providing a radio coverage area a plurality of subscriber units located within the radio coverage area, the plurality of subscriber units serviceable by a wideband communication resource selectively supporting uplink data packet transmissions from at least some of the plurality of subscriber units; means for determining a level of uplink loading of the wideband communication resource; and packet scheduling control logic responsive to the means for determining a level of uplink loading of the wideband communication resource, the packet scheduling control having:

means for assessing an availability of data packet resources supported by the wideband communication resource; and CE30809P-Offier means for causing selective notification of the availability of data packet resources to subscriber units requiring data packet transmissions.

10. The wideband communication system of claims 9, wherein the means for assessing the availability of data packet resources is operational responsive to an interference environment of at least a primary cell serving a subscriber unit arranged to support data packet transmissions.

11. The wideband communication system of claim 9 or 10, wherein the means for assessing the availability of data packet resources is operational responsive to a perceived level of signal propagation loss from cells other than a primary cell serving a subscriber unit arranged to support data packet transmissions.

12. The wideband communication system of claim 9, 10 or 11, wherein the means for causing selective notification of the availability of data packetresources is arranged to utilise a dedicated control channel to communicate the selective notification.

13. The wideband communication system of claim 12, wherein the means for causing selective notification of the availability of data packet resources is arranged to utilise a transport format combination (TFC) message of a dedicated -control channel to communicate the selective notification.

14. The wideband communication system of claims according to any of claims 9 to 13, wherein the to means for determining the level of uplink loading is arranged to monitor a plurality of cells and the means for assessing the availability of data packet resources is operational responsive to a highest traffic loading within the plurality of cells.

CE30809P-Villier

15. The wideband communication system of claims according to any of claims 9 to 14, wherein the packet scheduler is coupled to at least one of a radio network controller and a base station sub-system.

16. The wideband communication system of claims according to any of claims 9 to 15, wherein the wideband cellular communication system supports a code division multiple access protocol.

17. A method of scheduling up-link data packet transmissions on a wideband communication resource from subscriber units of a wideband cellular communication system containing at least one cell in which the subscriber units are located and wherein at least some of the plurality of subscriber units selectively require access to the wideband communication resource, the method comprising: determining a level of uplink loading of the wideband communication resource: assessing, in responsive to the level of uplink loading, an availability of data packet resources supported on the wideband communication resource; and causing selective notification of the availability of data packet resources to subscriber units requiring data packet transmissions.

18. The method of scheduling up-link data packet transmissions according to -clairn 17, further comprising: determining an interference environment of at least a primary cell serving a subscriber unit arranged to support data packet transmissions, and wherein assessing the availability of data packet resources is operational responsive to the interference environment.

19. The method of scheduling up-link data packet transmissions according to claim 17 or 18, wherein assessing the availability of data packet resources is operational responsive to a perceived level of signal propagation loss from cells CE30809P-WIlier other than a primary cell serving a subscriber unit arranged to support aata packet transmissions.

20. The method of scheduling up-link data packet transmissions according to 5 claim 17, 18 or 19, wherein causing selective notification of the availability of data packet resources further comprises utilising a dedicated control channel to communicate the selective notification.

21. The method of scheduling up-link data packet transmissions according to 10 claim 20, further including using a transport format combination (TFC) message of a dedicated control channel to communicate the selective notification.

22. The method of scheduling up-link data packet transmissions according to any of claims 17 to 21, wherein determining the level of uplink loading includes: monitoring a plurality of cells; determining a highest traffic loading within the plurality of cells; and - wherein assessing the availability of data packet resources is operational responsive to the highest traffic loading within the plurality of cells.

23. The method of scheduling up-link data packet transmissions according to any of claims 17 to 22, wherein the wideband cellular communication system supports a code division multiple access protocol.

24. A computer program element comprising computer program code means for making a controller execute procedure to perform the method steps of any of claims 17 to 23.

25. The computer program product of claim 24, embodied on a computer readable medium.

CE30809P-WIfier

26. A computer program product for a data packet scheduling function operational on a scheduling controller for a wideband cellular communication system containing at least one cell in which subscriber units are located, and wherein at least some of the subscriber units selectively require access to the wideband communication resource to support data packet transmissions, the computer program product comprising:

code that directs the scheduling controller to be responsive to a determination of a level of uplink loading on the wideband communication resource; code that directs the scheduling controller to assess, in responsive to the level of uplink loading, an availability of data packet resources supported on the wideband communication resource; and code that directs the scheduling controller to cause selective notification of the availability of data packet resources to subscriber units requiring data packet transmissions; wherein the codes reside in a computer readable medium.

27. A data packet scheduler (70) substantially as hereinbefore described with reference to the accompanying drawings.

28. A wideband cellular communication system substantially as hereinbefore described with reference to the accompanying drawings.

29. A method of scheduling up-link data packet transmissions (69) on a wideband communication resource, substantially as hereinbefore described with reference to the accompanying drawings.

30. A computer program element or a computer program product, substantially as hereinbefore described with reference to the accompanying drawings.