WO2005032181A1

WO2005032181A1 - Dynamic allocation of resources

Info

Publication number: WO2005032181A1
Application number: PCT/GB2004/004117
Authority: WO
Inventors: Timothy John Lunn; Alan Geoffrey Carr; Charles Donald; Diego Giancola
Original assignee: Pa Consulting Services Limited
Priority date: 2003-09-26
Filing date: 2004-09-27
Publication date: 2005-04-07
Also published as: GB0322624D0

Abstract

A participant for a wireless-communications network, comprising a plurality of digital signal processing units for performing elements of digital signal processing required by a signal and allocation means for dynamically allocating the elements to the units for processing.

Description

DYNAMIC ALLOCATION OF RESOURCES

The invention relates to participants in wireless communications networks, such as base stations and mobile telephones.

A wireless-communications network comprises one or more subscriber units and one or more base stations for conducting communications between subscriber units. Each base station will normally be capable of handling simultaneously calls made by a plurality of subscriber units in the vicinity of the base station. Typically, the subscriber units will be mobile telephones. The subscriber units can be termed "users" of the base stations.

Typically, a modern base station will perform some of its signal processing in the analogue domain and some of its signal processing in the digital domain. For example, in the context of signal reception by a UMTS (Universal Mobile Telecommunications System) base station, the analogue signal processing will usually comprise the down conversion of a received RF (radio frequency) signal to base-band with the digital signal processing involving the recovery of an information signal from the base-band signal by descrambling and despreading, etc. In the context of signal transmission by a base station, the digital signal processing will typically comprise the spreading and scrambling of an information signal with the analogue signal processing involving the modulation of the resulting spread-spectrum signal onto an RF carrier wave for transmission from an antenna. Obviously, the foregoing description gives only the briefest of outlines of how signal processing operations can be divided between the analogue and digital domains and many variations will exist. For example, it is possible for part of the conversion between base-band and RF to be done digitally by digitally converting a signal between base-band and IF (intermediate frequency) with the conversion between IF and RF being performed in the analogue domain.

In a so-called 3G (third generation) wireless communications network, for example a network conforming to the UMTS (Universal Mobile Telephone System) standards, the amount of digital signal processing that a base station has to perform on signals being sent to, and received from, users can be burdensome, particularly where the number of users serviced by a given base station is large.

Traditionally, the design proposed for a 3G base station requires hardware elements that are specifically designed to carry out particular digital signal processing tasks at high speed. However, it is also possible to provide a base station with one or more high-speed, general-purpose signal processors which can be programmed with appropriate software for carrying out the digital signal processing functions of the base station, including those that would be performed by the specially designed hardware elements in the traditional type of base station design. A base station of this type is sometimes referred to as a soft base station. Where a plurality of such general purpose signal processors are employed in a soft base station, they are often referred to collectively as the base-band processing resources of the soft base station since between them the processors have to carry out the majority of the base-band processing of the base station.

In a conventional soft base station, the signal processors forming the pool of base-band processing resources are each dedicated to the performance of a certain type (or types) of signal processing task. For example, consider a UMTS soft base station that receives signals that variously require code-despreading, correlation with synchronisation words and turbo-decoding. Some of the signal processors will be dedicated to perform despreading exclusively, others will be dedicated to perform exclusively synchronisation word correlation and yet others to perform just turbo-decoding.

For the purposes of illustration, Figure 1 shows the processing of six signals within a UMTS soft base station. Each of the signals is received at the base station from a different user U1-U6. Each of the signals undergoes similar processing within the soft base station and Figure 1 shows three of the main signal processing operations being performed on the signals. The triangles denote multi-path searching, the circles denote code-despreading by rake receivers and the squares denote turbo-decoding. Figure 2 demonstrates how signal processors in the conventional UMTS soft base station are dedicated to these operations. Figure 2 illustrates the base-band processing resources within the conventional soft base station, comprising three high-speed, digital signal processors (DSPs). DSP #1 is dedicated to multi-path searching and therefore undertakes such operations for the six users. DSP #2 is dedicated to rake receiver despreading and therefore undertakes such operations for the six users. DSP #3 is dedicated to turbo decoding and therefore undertakes such operations for the six users. It will be noted that this dedication of the DSPs to certain tasks is indicated in Figure 2 by the allocation of the triangle, circle and square symbols to the DSPs.

One aim of the invention is to provide a scheme for using processing resources within a participant for a wireless-communication network, such as a soft base station.

According to one aspect, the invention provides a participant for a wireless-communications network, comprising a plurality of digital signal processing units for performing elements of digital signal processing required by a signal and allocation means for dynamically allocating the elements to the units for processing.

The invention also consists in a method of performing base-band signal processing with a participant for a wireless-communications network, the participant comprising a plurality of digital signal processing units for performing elements of digital signal processing required by a signal, the method comprising dynamically allocating elements to the units for processing.

Thus, the invention provides a scheme wherein elements of digital signal processing are dynamically allocated to digital signal processing units for execution.

In one embodiment, the dynamic allocation is arranged to maximise the proportion of the collective processing capacity of the digital signal processing units that is in use at a given time, thereby enhancing the throughput of the units. In a preferred embodiment, the participant is soft base station, for example a UMTS soft base station. In another embodiment, the participant is a subscriber terminal, for example a mobile telephone.

By way of example only, some embodiments of the invention will now be described by reference to the accompanying drawings, in which:

Figure 1 illustrates, schematically, the concurrent processing within a UMTS base station of signals received from six distinct users;

Figure 2 illustrates, schematically, a conventional allocation of base-band processing tasks to DSPs in a soft base station;

Figure 3 illustrates, schematically, the allocation of base-band processing load to DSPs in a soft base station; and

Figure 4 illustrates in greater detail an example of dynamic allocation of tasks involved in base-band processing a channel received from a user by a soft base station.

The processing of multiple, concurrently-received signals within a UMTS base station was explained earlier with reference to Figure 1. Figure 3 illustrates how the processing tasks illustrated in Figure 1 are allocated to the base-band processing resources of a UMTS soft base station in an embodiment of the invention.

Figure 3 shows three digital signal processors DSP #1, DSP #2 and DSP #3. Between them the three DSPs perform all the base-band signal processing of the UMTS soft base station of the embodiment. A base-band resource management algorithm (RMA) within the base station is responsible for allocating to the DSPs the various base-band tasks required in the handling of the signals from users. The RMA is performed in response to various events, for example the addition to, or removal from, the base station of users or the reconfiguration of user signals (e.g. upon a switch to a different UMTS transport format). Consider the situation where a new user is to be supported by the base station. The RMA looks at the current usage of the processing resources within the DSPs to measure the spare processing capacity, if any, that each of the DSPs has. On the basis of the measured amount of spare processing capacity, the RMA allocates the base-band tasks of the new user to the DSPs in a manner that provides a best fit to the spare processing capacity. That is, the base-band tasks of the new user are allocated in a way that maximises the usage of the base-band processing resources offered by the DSPs.

Figure 3 shows how the RMA allocates the base-band tasks of the signals shown in Figure 1 to the three DSPs. During the course of processing the signals from users U1-U6, it transpires that the RMA allocates to DSP #1 the multipath searching for users Ul, U2, U3 and U5, rake receiver despreading for Ul and U5 and turbo decoding for Ul and U3; to DSP #2 the multipath searching for U4, rake receiver despreading for U3, U4 and U6 and turbo decoding for U2; and to DSP #3 the multipath searching for U6, rake receiver despreading for U2 and turbo decoding for U4, U5 and U6.

Figure 4a shows some of the base-band processing that might need to be performed in a UMTS base station on a signal received from a user. The base-band processing tasks shown in Figure 4 are DPCCH processing, TCFI processing, DPDCH processing and bit rate processing (e.g. for turbo decoding the signal received from the user). The DPCCH processing is for multipath searching (i.e. estimation of the channel power delay profile for use by finger detection/allocation and timing tracking algorithms), channel estimation (i.e. estimation of the gain and phase of the channel for the particular multipath component associated with a particular rake finger, for use in the finger combining algorithm), SIR estimation (i.e. estimation of the signal to interference ratio on a particular channel), BER estimation (i.e. estimating the fraction of the DPCCH bits that are received in error), power control (where the transmit power control bits embedded in the DPCCH are extracted in the receiver for controlling the power output for that channel by the transmitter) and transmit diversity feedback (where the closed-loop transmit diversity bits embedded in the DPCCH are extracted in the receiver for controlling the gain and phase of the transmitter's second "diversity" channel). The TCFI processing is for determining the traffic format applied by the user to the received signal. The DPDCH processing is for despreading the received signal to recover an estimate of the raw coded bits transmitted and combining the raw bit estimates from several multipath components to give a better estimate of the signal transmitted.

In a soft base station according to an embodiment of the invention, the base-band tasks shown in Figure 4a are allocated to the DSPs of the soft base station by the RMA. As a result, and as shown in Figure 4b, the DPCCH processing and the TFCI processing are performed sequentially on a digital signal processor, DSP#1. Once the TFCI processing has been completed, the RMA evaluates the base-band tasks that are waiting to be processed, i.e. the DPDCH processing and the bit rate processing. The RMA determines that for best usage of the available the base-band processing resources, the DPDCH processing is carried out on DSP #1 but the bit rate processing is now allocated to another digital signal processor, DSP #2.

Claims

1. A participant for a wireless-communications network, comprising a plurality of digital signal processing units for performing elements of digital signal processing required by a signal and allocation means for dynamically allocating the elements to the units for processing.

2. A participant according to claim 1, wherein the allocation means is arranged to allocate elements for processing in a manner which optimises the throughput of the units.

3. A method of performing base-band signal processing with a participant for a wireless-communications network, the participant comprising a plurality of digital signal processing units for performing elements of digital signal processing required by a signal, the method comprising dynamically allocating elements to the units for processing.

4. A method according to claim 3, wherein said dynamic allocation is arranged to allocate elements for processing in a manner which optimises the throughput of the units.

5. A participant for a wireless-communications network, substantially as hereinbefore described with reference to Figure 3 or 4.

6. A method of performing base-band signal processing with a participant for a wireless-communications network, substantially as hereinbefore described with reference to Figure 3 or 4.