GB2419046A

GB2419046A - Predicting and automatic gain control value in a mobile communications device

Info

Publication number: GB2419046A
Application number: GB0422184A
Authority: GB
Inventors: Hamid Falaki; Rakesh Chauhan; V B Manimohan
Original assignee: NEC Technologies UK Ltd
Current assignee: NEC Technologies UK Ltd
Priority date: 2004-10-06
Filing date: 2004-10-06
Publication date: 2006-04-12
Anticipated expiration: 2024-10-06
Also published as: GB0422184D0; GB2419046B

Abstract

A system for selecting an initial value for an automatic gain control (AGC) signal is disclosed. The system may be applied where at least two base stations (BTS) communicate with a mobile unit, including 2G (GSM) and 3G (UMTS) networks. Each base station includes means for transmitting a signal including location co-ordinates and power level data of the at least two base stations. The mobile device includes means for receiving the signal from a first base station and means for measuring the received power level from the first base station. The mobile device also includes means, such as a global positioning system (GPS) receiver, for determining its own location. The mobile includes means for periodically receiving signals from a second base station, e.g. during transmission gap lengths (TGLs). The mobile then predicts the initial AGC value to apply to signals received from the second base station in dependence on the relative locations of the mobile device and the first and second base stations, the received power level of the signal from the first base station and the known transmission power of the first and second base stations. The system allows a 3G / 2G dual mode terminal to switch to GSM. The faster AGC action increases battery life.

Description

A SYSTEM FOR PREDICTING AN AUTOMATIC GAIN CONTROL

VALUE

The present invention relates to a system for predicting an automatic gain control value and, in particular, to such a system incorporated in a mobile communication device.

In operation, a mobile communication device sets up a primary communication link with a serving base station (BTS). Network information and calls are received in signals from the serving base station. During communication with the serving base station, the device monitors signals from neighbouring base stations in case a BTS handover is required. A handover may be required when, for example, a signal from a neighbour base station is stronger than that from the serving base station or if the communication link between the BTS and mobile communication device is interrupted due to technical problems in the base station or because the mobile communication device moves out of range. The mobile communication device monitors signals from neighbour base stations during breaks in communication with the serving base station, Here we call these breaks transmission gap lengths (TGLs) either in 2G or 3G.

The procedure of monitoring neighbour base stations is relevant to all mobile communication technologies including second and third generation (2G and 3G) systems. As 3G networks are introduced, it is expected that the 3G networks will be overlaid with 2G networks. The users will be spread between both networks depending on user priority, service requested, coverage and other operator strategies on the use of network resources. During a call, a terminal which is capable of both 3G (UNITS) and 2G (GSM) dual mode type operation may use the transmission gaps to measure GSM cells during a UMTS call since it may need to switch to GSM.

During communication with the serving BTS, TGLs are short and well defined, particularly in UNITS networks. At the end of the TGL the mobile communication device must recommence communication with the serving BTS.

When a signal is received from any base station the mobile communication device applies an Automatic Gain Control (AGC) to amplify the received (RX) signal. The value of the AGC is fed to the receive block of the mobile communication device to optimise the digital dynamic range of its receiver's sensitivity to match the receiving signal radio frequency. It is important that the AGC value is set correctly in order that all information from the signal can be decoded and monitored by the mobile communication device. If the AGC value is too low, the signal is not amplified sufficiently and some of the information from the signal will not be identified by the mobile communication device. Alternatively, if the AGC value is too high then the signal is saturated during the amplification process and information from the signal will be lost.

The correct AGC value for a particular received signal depends on the RX power level of the received signal. The RX power level is dependent on many factors including the transmission (TX) power level from the BTS, the distance between the BTS and the mobile communication device and the degradation of the signal due to obstacles between the BTS and mobile communication device. The combined effect of these factors means that the signals from different BTS require different AGC values. Additionally, as the device moves, the AGC value associated with a particular BTS may need to be adjusted.

Typically, systems identify the correct AGC value by performing an AGC search in which the AGC value is increased or decreased systematically until the correct value is obtained. Improved systems make an initial guess of the required value, the guess being the value that was used the previous time that a signal was received from that particular BTS.

The device then increases or decreases the AGC value from the initial guess until the correct value is found.

However, a problem with using the previously stored value as the initial AGC value is that the value will only be correct if the RX power level at the mobile communication device is the same in subsequent transmissions. This will only be the case if the distance between the base station and the mobile communication device and the degradation in signal have not changed since the previous measurement. In fact, if the device is moving quickly then the required AGC value may have changed significantly since the last measurement. Although the device will eventually find the correct value, the previous value is only good for slow moving or stationary users otherwise if the end user is moving rapidly the search may take time. This becomes even more important when the end user is travailing at high speed and is continually changing neighbour cells lists. This means making measurements on new cells that the handset has no previous AGC values.

If the AGC value has changed significantly since the last measurement, a relatively large part of the TGL is taken up searching for the correct AGC value. This reduces the time available for measurements and draws a large amount of power.

We have appreciated that it is important to receive signals from neighbour BTS and that the AGC value for a received signal must be set correctly in order that all information from the signal can be analysed by the mobile communication device. We have also appreciated that the opportunities for receiving these signals (TGLs) are short in duration.

Therefore, in order to provide the maximum time for taking measurements on the incoming signal, it is important to reduce the time taken to determine the correct AGC value.

Embodiments of the present invention reduce the time taken for the AGC search by predicting the required AGC value based on the current conditions when the signal is received. The RX power level is predicted by determining the physical distance between the device and BTS, knowing the TX power level of the signal from the BTS and accounting for the degradation in signal due to obstructions. By predicting the value based on the present conditions the mobile communication device provides a more accurate initial AGC value than using the previous value. Thus the time taken to find the correct AGC value is reduced.

Embodiments of the invention enable the AGC value to be calculated by transmitting coordinates of local base stations and the transmission power of signals from those base stations.

The invention is now defined in its various aspects in the claims to which reference should now be made.

An embodiment of the invention is now described in detail with reference to the accompanying figures in which: Figure 1 is a representation of a cell network including 2G GSM cells and 3G UMTS cells.

Figure 2 is a flow diagram showing the steps taken when implementing embodiments of the present invention.

Figure 3 shows the flow of information in transmissions between the handset and various base stations.

Figure 4 shows how the measurement opportunities are used in known systems.

Figure 5 shows how the measurement opportunities are used and Figure 6 is a block diagram showing the components required by a handset for use in an embodiment of the present invention.

Figure 1 shows a mobile communication device which is capable of communicating on a 2G GSM network and a 3G UMTS network. The mobile communication device 10 is in the locality of 3 GSM cells, namely, GSM1, GSM2, GSM3 and a UMTS cell, namely, UMTS1. Network coverage in each GSM cell is provided by base station BTS1, BTS2 and BTS3 respectively and in the UMTS cell by node B. It should be appreciated that Figure 1 is an example of a mobile communication device in communication with local base stations and, in practice, the device may be able to communicate with additional GSM base stations or UTMS nodes.

The following description describes the situation in which the mobile communication device is communicating with node B as the serving node on the 3G, UMTS network. The base stations BTS1, BTS2 and BTS3, associated with GSM cells GSM 1, 2 and 3 respectively, are local non- serving base stations and the device monitors signals from these base stations periodically. This arrangement of non-serving and serving base stations is provided as an example and it is understood that the invention is equally appropriate to the case in which the serving base station is a GSM base station and when the invention is implemented in a device operating in a purely (GSM) or 3G (UMTS) network.

Figure 2 is a flow diagram showing the steps taken in order to implement embodiments of the present invention. In the example of Figure 2, the handset has set up a primary communication link with a serving node. At 200 the serving node transmits co-ordinates of neighbour base stations and nodes and also transmits the power at which signals are transmitted from those base stations and nodes (TX power level). The node also transmits its own coordinates and its own TX power level. This information should be transmitted as part of the standard transmission cycle. Therefore, each base station and node are aware of the co- ordinates and transmission power of all neighbouring base stations and nodes in addition to its own location and TX power level. Preferred embodiments of the invention will transmit co-ordinates and transmission power of all neighbouring network antennas including 2G base stations and 3G nodes. However, further embodiments of the invention may only transmit information relating to transmissions from 2G base stations or, instead, only transmit information relating to 3G nodes. Preferred embodiments of the present invention transmit the location and transmission power of neighbour base stations and nodes periodically as part of the standard transmission cycle.

At 210 the transmission from the serving node is received at the mobile communication device. The mobile communication device may process the information immediately or, alternatively, store the information relating to the neighbouring base stations and nodes in its memory. At 220 the device determines whether it wishes to receive signals from a non- serving base station or node. If it does wish to receive these signals, they must be received during a break in communication with the serving node.

If the device wishes to receive signals at 220, it determines its present location at 230. Preferred embodiments of the invention determine their location using GPS system or other means of determining location. The mobile communication device is now aware of its own location as well as the locations of the node of the serving cell and the base stations for nelghbouring, non-serving, cells.

In order to calculate the RX power level of the signals from the non serving base station the device first calculates the distance between itself and the serving BTS at 240. The device then calculates the path loss associated with the signal from the serving node at 250. The path loss is the degradation in strength of a signal from transmitter to a receiver. This loss is due to the physical distance between the transmitter and receiver as well line of sight obstacles positioned between the transmitter and receiver, for example buildings, trees and surface roughness. The device is able to calculate the path loss associated with the signal from the serving base station since it knows the TX power level of the signal from the serving BTS, the RX power level (measured by the mobile communication device) and the physical distance between the serving node and the mobile communication device.

The mobile communication device now calculates the expected RX power level of the signal from a neighbour BTS. The mobile communication device has already been provided with the co-ordinates of the non-serving base station that it wishes to monitor and has determined its own coordinates. Using these known coordinates it determines the distance between the neighbour BTS and the mobile communication device at 260. The mobile communication device now uses the path loss associated with the signal from the serving BTS, the distance between itself and the neighbour BTS and the TX power of the signal from the neighbour BTS to calculate the expected RX power level of signals from that BTS.

The following equation describes the relationship between the received power levels, transmit power levels and the distance of the handset from the base stations, in the fog domain.

PrXIGSM-PrX WCDMA = (P b(,GSM-P WCDMA) + O(dWCDMA-d GSM) + K In the equation, Pr> refers to the received power level of the signal at the handset, Pa refers to the power of the signal when transmitted from the BTS and d is the distance between the handset and the base station. The constants a and K are tunable parameters. These parameters are set dependent on the operating frequency and the network terrain. These parameters are needed to calibrate the process. a converts the unit of distance to RF power (using empirical correlations or data), and K IS a constant used for optimization of this principle. Using the above equation, the handset is able to estimate the received signal strength of the signal from the non-serving base station (Pr,CGSM) at 270.

Once the estimated received power level has been calculated the handset is able to compare this level with the reference target for the AGC level, ie the amplitude to which the incoming signal is required to be magnified in order that all information in the signal is received. A simple comparison of the reference amplitude with the estimated received power level provides the handset with the required AGC value for a signal received from that particular non-serving base station at 280.

Now the device has made an estimate for the required AGC value associated with the incoming signal, the device receives the signal from the selected neighbouring base station during a TGL at 290.

In some cases, the initial AGC level for the signal received from the neighbouring base station may require a small adjustment. Reasons for error in AGC value include movement of the mobile communication device when the distance between the device and the base station is changing rapidly. Also, the equation for predicting the received power of the signal from the neighbouring base station assumes that the path loss per unit distance is the same for signals between the serving base station and the handset as the non-serving base station and the handset. In practice, the path loss may be slightly different due to different obstacles on the signal path. If the initial value is slightly incorrect the device adjusts the AGC value at 300 in order to meet the reference target for the AGC value.

Although the initial AGC value may not require minor adjustment, the estimated value is likely to be very close to the required value and so only minor adjustment of the AGC value will be required. In contrast, present systems which use the previous value in a fast fading environment (e.g. travailing along a high way) usually require a significant adjustment.

Therefore a large time and, hence, power saving is provided by embodiments of the present invention.

Figure 3 shows the transfer of data between the network, base stations and nodes and layers mobile communication device. In Figure 3, the device has set up a communication link on the UMTS network (Radio Access Technology (RAT) 1) and receives signals from its serving node (node B). These signals are received from the node B1 at the lower layers of the mobile communication device at 310. At the same time, the GSM network which operates on RAT2 is transmitting signals from base station BTS1 which are also available for receipt by the mobile communication device at 300. Step 320 indicates that the signals transmitted by the network from both node B1 or base station BST1 include information including the neighbour cell frequency, the X Y and Z location co- ordinates of the serving node or base station, the co-ordinates of neighbouring base stations or nodes and the transmission power of signals from both the serving base station or node and neighbour base stations or nodes. This information is transmitted as part of the transmission cycle during normal communications and can be stored within the device.

When the mobile communication device is required to receive a transmission from a neighbour base station it first obtains its location from a GPS system (or equivalent) at 330. At 340 the device is informed of its co-ordinates. Once the device is aware of its co-ordinates, it calculates the distance to the serving node B1, the path loss on the signal from node B1, the distance to the BTS and the expected RX power level of the signal received from the neighbour BTS. The device then estimates the required AGO value at 350. This information is transmitted to the lower layers of the device and an initial AGO value is set for RAT2 at 360. At 370 the device receives signals from RAT2 from base station BTS1 and these measurements are reported to the higher levels of the device at 380.

Figure 4 shows the operations performed by a mobile communication device operating in a known system during a measurement opportunity. In Figure 4 the lower layers of the mobile communication device request to receive signals from a first neighbouring base station on frequency 1 at a time T1. At T1 the receive block of the mobile communication device is activated and the device begins to monitor incoming signals on that frequency. The receive block is only available for a predetermined period (T1 - T2) since the MDC resumes communication with the serving BTS at T2.

Once the receive block is activated at T1, the device begins to execute an AGC control search 420. Typically, the mobile communication device will increase the sensitivity of the AGC gradually in order to find the required AGC value. At 430 (T3) the device identifies the AGC value associated with the RX signal. At 440 (T4), the device sets the AGC value accordingly and begins to take measurements on the signals from the neighbour base station. Typically, there will be a short time delay between identifying the required AGC value and commencing amplification of signals at that value. As shown in 440, measurements begin at T4. The first signals on frequency 1 are received at T5 as shown in 450.

Therefore, the time period during which measurements can be taken runs between T5 and T2. Figure 4 demonstrates that, in known systems, there is a time delay of T1 to T3 during which the RX block is available but during which no measurements are taken.

Figure 5 shows the operations performed by a mobile communication device operating in an embodiment of the present invention during a measurement opportunity equivalent to that shown in Figure 4. At 500 the lower layers of the mobile communication device instruct the device to receive signals on a first frequency at a time T10. At T10 the receive (RX) block is activated for a period defined by the measurement window T10 to T11. At 520, T11, the handset makes an initial estimate of the required AGC value based on the location of the serving and non-serving base stations, the location of the handset and the path loss on the signal from the serving BTS as discussed above. At 530, T12, the AGC value is set and the mobile communication device determines whether the estimated AGC value will be correct for the incoming signal. In particular situations the predicted AGC value will be correct and the measurement opportunity will begin, however, in some situations the predicted AGC value may be slightly incorrect and will need to be adjusted. This is an optional stage that can be removed if the accuracy of the initial AGC meets the acceptable dynamic range of the RSSI. At T13 the correct AGC value is determined. Note that if the initial estimate of the AGC value is correct T12 and T13 will coincide. Once the AGC value is correct at T13, the time period for measurements of the signal from the neighbouring base station commences at 550. At a short time later, T14, the mobile communication device receives the transmission on the first frequency. The mobile communication device completes the required measurements at T15.

It can be seen from a comparison of the time frames shown in Figures 4 and 5 that the period for measurements on the neighbour cell, having determined the correct AGC value, begins much earlier in embodiments of the present invention than in conventional systems, is T13 compared with T4 Since the correct AGC value is identified sooner, a larger part of the measurement opportunity window can be used to take measurements on the neighbour base station. There are several advantages associated with identifying the correct AGC value sooner, including the fact that there is less pressure on the device to receive all required measurements in the available time frame, for example in Figure 4 if the measurements on the non-serving base station are not complete by T2 the handset must close its RX window for frequency 1 in order that it can recommence communication with the serving base station on node 1.

Furthermore, once the measurements are complete the device can either take further measurements or move into a sleep for the remainder of the measurement period and, thus, save power.

Figure 6 is a block diagram showing the components required in a handset for operation in a system implementing the present invention. The handset 600 includes an antenna 610 for transmitting and receiving signals from local base stations or nodes. Preferred embodiments of the invention include an aerial suitable for operation on both a 2G or 3G networks. The device includes a clock 620 for controlling the timing of transmission and reception of signals. The central processing unit 640 has access to all the information from memory block 660. The information is passed to the functional block 630 to derive the Automatic Gain control and pass this to the Analogue RF block 715 to set its receiver amplification accordingly. The object is to ensure full digitization range of the ADC block 725 is used when converting the analogue signal to digital format for further processing. The CPU is also linked to a RF frequency tuner 680 to control the frequency at which signals are received. The device memory 660 stores the locations and transmission powers of local base stations.

This information is provided to the device in the transmissions received from the serving base station. The mobile communication device also includes a location determining means, for example a GPS, 670 in order that it can calculate the distance between itself and the serving and non serving base stations.

It will be clear to those skilled in the art that the present invention provides a system in which an accurate initial estimate can be made of the required AGC value for signals received from a particular neighbour base station. Embodiments of the invention enable the correct AGC value to be determined in a much shorter time than in known systems. By decreasing the time taken to determine the AGC value associated with an incoming signal, the mobile communication device is able to make better use of the measurement opportunities by increasing the number of measurements taken during the measurement period or by reducing power consumption of the mobile communication device.

We now provide an example of an embodiment of the present invention operating in the UMTS access stratum in order to illustrate the power saving potential of embodiments of the present invention. The following relates to UMTS mobile equipment operating in an idle mode.

In the idle mode there are three main processes, namely PLAIN (network) selection, cell selection and re-selection and Local Registration.

In the idle state mobile equipment spends most of its time in the cell selection and re-selection state. For this reason, we focus this example of the power saving provided by embodiments of the present invention to the cell selection and re-selection cell state of idle mode operation. In this state, the mobile communication device periodically measures the received signal strength of signals from the serving cell. The list of channels scanned is given to the mobile by the network.

The benefit of the embodiments of the present invention is demonstrated by the comparison between the time periods shown in Figure 4 and Figure 5. In known equipment the AGC search for identifying the correct AGC value for a particular signal may take as much as 0.66 ms. On a conservative assumption the present invention will reduce this period by 50% i.e to 0.33ms.

The AGC procedure is performed to derive the receiver gain for the selected frequency. Once this is set, the signal is digitised and the power level is measured as an index defined by standards for reporting to the higher layers and or possibly back to the network. This typically takes 0.066ms and is known as RX-Lev or RSSI. . The current drawn by the handset in the AGC procedure and during the RSSI evaluation is roughly the same. Thus the energy taken over the entire cycle is (0.33 + 0.066)/(0.66 +0.066)= 54% of what it was before. Thus the energy saved during this operation is 46%. However, as discussed earlier, known systems often use the AGC value which was used on the previous time the device received a signal from that neighbouring base station.

Therefore, not every RSSI measurement will require an AGC search to be run. Typically, only those occasions where the base station to handset separation has changed by an appreciable amount since the last measurement will require a new AGC search to be executed. In dynamic use the proportion of such measurements increases with increasing speed, however the relationship is highly non linear. Considering an average over all speeds, approximately 95% of the RSSI measurements will execute a new AGC search and, therefore, the practical saving is reduced to around 46% x 95% = 44%.

We must also consider that not all of the power consumption of a handset in the idle mode is due to monitoring. In fact, a large proportion of the power consumption is due simply to leakage currents. In existing handsets the leakage takes up to 50% of the total drain. Taking this "baseline" current into account, the saving produced by the new method is 44% X 50% = 22%.

It should be noted that as device technology improves the leakage current will steadily decrease. Therefore, embodiments of the present invention will become steadily more effective in saving power.

Typically, the battery power will last half as long in a dynamic environment as it does in a static environment. Typical battery life in dual mode handsets is around 150 hours in a static idle state. Thus, in a dynamic environment, eg in a moving vehicle, battery life may be as little as 75 hours. Therefore if the example described above were to be implemented, a significant improvement could be achieved. At a rough approximation this would be 75 hours x 22% in a dynamic environment.

This calculation indicates an increase of 16.5 hours standby time in a dynamic environment.

The 22% figure is applicable to the FDD radio access technology and current device technology as indicated above in the text of the application. Other radio technologies such as UMTS-TDD or TD-CDMA may also benefit greatly by incorporating the embodiments of the present invention.

In a further example, two RSSI measurements are made per paging cycle, one with a known AGC (cell already camped on) and the other with an unknown AGC. Using a time of 0.66ms taken by the AGC algorithm, 0.066ms for one RSSI measurement, and using the assumption that the invention reduces the AGC algorithm time period by 50%, this produces a gain of about 1(0.33ms+2xO.066ms)/(0.66ms + 2xO.066ms) = 41%.

Thus we can assume about 40% of the reduction in power consumed in evaluating the initial gain value for a cell just added to the neighbour cell list.

In summary this principle has advantage when a new cell's RSSI needs to be measured and saves about 40% time or power in this RSSI measurement.

When the mobile is stationary; first time the list of all neighbour cellsare given to the mobile. This algorithm may be used and gain some time in the operation, hence some small amount battery power may be saved every time the handset is powered up. The AGC values derived first time are then used in the following cycles as the initial conditions for the AGC and this leads to no more time gained by using this principle. Overall when the mobile is stationary the battery saved is not significant using this method.

In the dynamic condition, the mobile is moving across cells and regularly receives updated list of neighbour cells and needs to find these cells and go through a cell re-selection algorithm. The list of neighbour cells can be as much as 32, however only a few of these are measured during the paging interval. In a standard implementation the power consumption of the mobile increases greatly resulting in lower battery life. This dynamic state involves some percentage of the time for measuring the new cells becoming RF visible and some percentage of the time actually transmitting / receiving and camping on a new cell. Statistically we can argue in a dynamic condition for a number of paging cycles, the mobile will encounter a ratio of 1 cell reselection in every 20 new cell RSSI measurement.

Hence in the ratio of 19/20 paging events or 95% of the time we can expect the benefit of this algorithm when there is no cell re-selection.

Typically, the terminal battery will last half as long in a dynamic environment as it does in a static environment. Typical battery life of our current dual mode handsets is 150 hours in static idle state. Thus, in a dynamic environment (e.g. in a vehicle), battery life may be as little as 75 hours.

If the proposal described above were to be implemented a significant improvement could be achieved. At a rough approximation, this would be (75hr dynamic environment) x (95% when the method is applicable) x (40% advantage in new cell's RSSI measurement). This calculation indicates an increase of 28.5 hours standby in dynamic environment - a gain of 38%.

The 38% figure is applicable to the FDD radio access technology indicated in the text of the application. Other radio access technologies such as UMTS-TDD or TD-CDMA may also benefit greatly from the use of this principle.

It will be clear to those skilled in the art that an important aspect of the present invention resides in the fact that the co-ordinates and transmission power of all local base stations in the neighbour list are transmitted by each base station along with the coordinates and TX power of the serving cell. In the case of known UMTS FDD networks, cell system information holds the information about neighbour cells. Currently, SIB 11 provides BSIC, frequency band and absolute radio frequency information about neighbouring (GSM or other RATS) cells to be measured. However, embodiments of the invention will require that the SIB 11 or other SIB information is to be extended to include additional network parameters for GSM neighbour cells, specifically the co-ordinates of the base station and the transmission power of signals from that base station.

The radio resources location protocol (RRLP) specifications from 3GPP provide cell co-ordinates as alternative to additional standardization for SIB11 of the 3GPP radio resource control (RRC) specification.

However, embodiments of the invention still require information about the transmission power of local base stations. Therefore, the standard for the UMTS network will require modification to SIB11 or other SlBs to include the information required by the embodiments of this invention.

Claims

1. A system for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device, the system comprising at least two base stations and at least one mobile communication device; each base station comprising: means for transmitting a signal including location coordinates of the at least two base stations and data defining the transmission power from each base station; the mobile communication device comprising: means for receiving the signal from a first base station; means for measuring the received power level of the signal from the first base station; means for determining the location of the mobile communication device; means for periodically receiving signals from a second base station; and means for predicting the initial AGC value to apply to signals received from the second base station in dependence on the relative locations of the mobile communication device and first and second base stations, the received power level of the signal from the first base station and the transmission power of the first and second base stations.

2. A signal suitable for transmission in a mobile communication network including; location data for at least two local base stations; and transmission power levels of signals from each of the at least two base stations.

3. An apparatus for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device, comprising: means for receiving a signal from a first base station, the signal including location coordinates of the first base station and at least one further base stations and data defining the transmission power from each base station; means for measuring the received power level of the signal from the first base station; means for determining the location of the mobile communication device; means for periodically receiving signals from the at least one further base station; and means for predicting the initial AGC value to apply to signals received from the at least one further base station in dependence on the relative locations of the mobile communication device and first and further base stations, the received power level of the signal from the first base station and the transmission power of the first and further base stations.

4. An apparatus for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to claim 3 wherein the means for predicting the initial AGC value includes a means for calculating the distance from the mobile communication device to the first and second base stations using the received coordinates of the base stations and the determined location of the device.

5. An apparatus system for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to claim 4 wherein the means for predicting the initial AGC value includes a means for calculating a reduction in power level per unit distance of the signal from the first base station using the received data defining the transmitted power level and the calculated distance between the device and the base station.

6. An apparatus for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to claim wherein the means for predicting the initial AGC value includes a means for calculating a reduction in power level of signals from the second base station using the reduction in power level of the signal from the first base station and the distance to the second base station.

7. An apparatus for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to claim 6 wherein the means for predicting the initial AGC value includes a means to predict the received power level of signals from the second base station using the transmission power level of signals from the second base station and the reduction in power level of signals from the second base station.

8. An apparatus for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to claim 7 including a means for predicting the AGC value in dependence on the predicted receive power level of signals from the second base station.

9. An apparatus for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to any of claims 3 to 8 wherein the means for determining the location of the mobile communication device is a GPS system.

10. An apparatus for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to any preceding claim wherein the AGC value can be adjusted after the initial value has been applied.

11. An apparatus for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device substantially as herein described with reference to the accompanying figures 1, 2, 3, 5 and 6.

12. A method for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device, comprising the steps of: transmitting a signal from at least two base stations including location coordinates of the at least two base stations and data defining the transmission power from each base station; receiving the signal from a first base station at a mobile communication device; measuring the received power level of the signal from the first base station; determining the location of the mobile communication device; periodically receiving signals from the at least one further base station; and predicting the initial AGC value to apply to signals received from the second base station in dependence on the relative locations of the mobile communication device and first and second base station, the received power level of the signal from the first base station and the transmission power of the first and second base stations.

13. A method for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device, comprising the steps of: receiving a signal from a first base station, the signal including location coordinates of the first base station and at least one further base stations and data defining the transmission power from each base station; measuring the received power level of the signal from the first base station; determining the location of the mobile communication device; periodically receiving signals from the at least one further base station; and predicting the initial AGC value to apply to signals received from the at least one further base station in dependence on the relative locations of the mobile communication device and first and further base stations, the received power level of the signal from the first base station and the transmission power of the first and further base stations.

14. A method for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to claim 13 wherein the step of predicting the initial AGC value includes a the step of calculating the distance from the mobile communication device to the first and second base stations using the received coordinates of the base stations and the determined location of the device.

15. A method for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to claim 14 wherein the step of predicting the initial AGC value includes the step of calculating a reduction in power level of signals from the second base station using the reduction in power level of the signal from the first base station and the distance to the second base station.

i6. A method for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to claim 5 wherein the step of predicting the initial AGC value includes the step of predicting the received power level of signals from the second base station using the transmission power level of signals from the second base station and the reduction in power level of signals from the second base station. .

il. A method for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to claim 6 ' including the further step of for predicting the AGC value in dependence. . on the predicted receive power level of signals from the second base. If, station.

i8. A method for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to any of claims l: to il wherein the step of determining the location of the mobile communication device is performed by a GPS system.

i9. A method for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to any of claims 12-18 including the further step of adjusting the AGC value after the initial value has been applied.

:0. A method for selecting an initial value for an automatic gain control (AGO) signal in a mobile communication device substantially as herein described with reference to the accompanying figures 1, 2, 3, 5 and 6. ë e . c . a.. .

15. A method for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to claim 14 wherein the step of predicting the initial AGC value includes the step of calculating a reduction in power level per unit distance of the signal from the first base station using the received data defining the transmitted power level and the calculated distance between the device and the base station.

16. A method for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to claim 15 wherein the step of predicting the initial AGC value includes the step of calculating a reduction in power level of signals from the second base station using the reduction in power level of the signal from the first base station and the distance to the second base station.

17. A method for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to claim 16 wherein the step of predicting the initial AGC value includes the step of predicting the received power level of signals from the second base station using the transmission power level of signals from the second base station and the reduction in power level of signals from the second base station.

18. A method for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to claim 17 including the further step of for predicting the AGC value in dependence on the predicted receive power level of signals from the second base station.

19. A method for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to any of claims 13 to 18 wherein the step of determining the location of the mobile communication device is performed by a GPS system.

20. A method for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to any of claims 13-19 including the further step of adjusting the AGC value after the initial value has been applied.

21. A method for selecting an initial value for an automatic gain control (AGO) signal in a mobile communication device substantially as herein described with reference to the accompanying figures 1, 2, 3, 5 and 6.

Amended claims have been filed as follows

1 A system for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device, the system comprising at least two base stations and at least one mobile communication device; each base station comprising means for transmitting a signal including location coordinates of the at least two base stations and data defining the transmission power from each base station; the mobile communication device comprising means for receiving the signal from a first base station; means for measuring the received power level of the signal from they'd first base station; . ...

means for determining the location of the mobile communication..

device; : means for periodically receiving signals from a second base station; - . and . means for predicting the initial AGC value to apply to signals received from the second base station in dependence on the relative locations of the mobile communication device and first and second base stations, the received power level of the signal from the first base station and the transmission power of the first and second base stations is 2. An apparatus for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device, comprising: means for receiving a signal from a first base station, the signal including location coordinates of the first base station and at least one furthe! base stations and data defining the transmission power from each base station; means for measuring the received power level of the signal from the first base station; means for determining the location of the mobile communication ë-- device; - means for periodically receiving signals from the at least one further base station; and means for predicting the initial AGC value to apply to signals received from the at least one further base station in dependence on the. . relative locations of the mobile communication device and first and further base stations, the received power level of the signal from the first base station and the transmission power of the first and further base stations.

3. An apparatus for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to claim wherein the means for predicting the initial AGC value includes a means for calculating the distance from the mobile communication device to the first and second base stations using the received coordinates of the base stations and the determined location of the device.

4. An apparatus system for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to claim 3 wherein the means for predicting the initial AGC value includes a means for calculating a reduction in power level per unit distance of the signal from the first base station using the received data defining the transmitted power level and the calculated distance between the device and the base station.

5. An apparatus for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to claim 4 wherein the means for predicting the initial AGC value includes a means for calculating a reduction in power level of signals from the second base station using the reduction in power level of the signal from the first base A. station and the distance to the second base station. ...

6. An apparatus for selecting an initial value for an automatic gain .

control (AGC) signal in a mobile communication device according to claim : wherein the means for predicting the initial AGC value includes a means....

to predict the received power level of signals from the second base station.

using the transmission power level of signals from the second base station and the reduction in power level of signals from the second base station.

7 An apparatus for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to claim 6 including a means for predicting the AGC value in dependence on the predicted receive power level of signals from the second base station.

8. An apparatus for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to any of claims 2 to wherein the means for determining the location of the mobile communication device is a GPS system.

9. An apparatus for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to any preceding claim wherein the AGC value can be adjusted after the initial value has been applied.

10. An apparatus for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device substantially as herein described with reference to the accompanying figures 1, 2, 3, 5 and 6.

At. A method for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device, comprising the steps of: transmitting a signal from at least two base stations including, location coordinates of the at least two base stations and data defining the .

transmission power from each base station; ...

receiving the signal from a first base station at a mobile communication device; measuring the received power level of the signal from the first base station; determining the location of the mobile communication device; periodically receiving signals from the at least one further base station; and predicting the initial AGC value to apply to signals received from the second base station in dependence on the relative locations of the mobile communication device and first and second base station, the received power level of the signal from the first base station and the transmission power of the first and second base stations.

i2. A method for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device, comprising the steps of: receiving a signal from a first base station, the signal including location coordinates of the first base station and at least one further base stations and data defining the transmission power from each base station; measuring the received power level of the signal from the first base station; determining the location of the mobile communication device; periodically receiving signals from the at least one further base station; and;. . predicting the initial AGC value to apply to signals received from the at least one further base station in dependence on the relative locations of,, the mobile communication device and first and further base stations, the A. ..

received power level of the signal from the first base station and the transmission power of the first and further base stations. I. 13. A method for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to claim i: wherein the step of predicting the initial AGC value includes a the step of calculating the distance from the mobile communication device to the first and second base stations using the received coordinates of the base stations and the determined location of the device.

14. A method for selecting an initial value for an automatic gain control (AGC) signal in a mobile communication device according to claim 13 wherein the step of predicting the initial AGC value includes the step of calculating a reduction in power level per unit distance of the signal from the first base station using the received data defining the transmitted power level and the calculated distance between the device and the base station.