GB2356527A - Power control in a CDMA network - Google Patents
Power control in a CDMA network Download PDFInfo
- Publication number
- GB2356527A GB2356527A GB9927200A GB9927200A GB2356527A GB 2356527 A GB2356527 A GB 2356527A GB 9927200 A GB9927200 A GB 9927200A GB 9927200 A GB9927200 A GB 9927200A GB 2356527 A GB2356527 A GB 2356527A
- Authority
- GB
- United Kingdom
- Prior art keywords
- network
- cells
- gain
- adjustments
- base stations
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
- H04W52/30—TPC using constraints in the total amount of available transmission power
- H04W52/34—TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading
- H04W52/343—TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading taking into account loading or congestion level
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
- H04W16/02—Resource partitioning among network components, e.g. reuse partitioning
- H04W16/06—Hybrid resource partitioning, e.g. channel borrowing
Abstract
A technique to balance the load across a CDMA network and hence increase its capacity for a given network grade of service (GoS). The technique applies varying uplink and downlink attenuation factors to the cells in the network, in order to change their effective coverage area. This has the effect of changing their load (or carried traffic) and hence the level of interference experienced by the cells. In this way, the carried traffic is forced to be redistributed uniformly across the cells and is of particular importance in a non-homogeneous network. The level of attenuation applied can be determined using an adaptive/optimisation algorithm either dynamically in real-time at network level or as part of the radio planning process of a CDMA/UMTS network. The source of data used to obtain the attenuation factors may be derived using system simulation and/or real network data.
Description
2356527 CDMA MOBILE COMMUNICATIONS This invention relates to mobile
communication systems deployed in a manner based on Code Division Multiple Access (CDMA) or 'spread spectrum' technology.
CDMA is a means of transmission in which, over time, the transmitted signal occupies a bandwidth in excess of the minimum necessary to send the information. The 'spread' is accomplished by transmitting data encoded on a relatively io narrowband signal at frequencies which are varied in a predetermined way and according to a predetermined pseudorandom code. The code is independent of the data and the frequency variations occur at a much higher rate than the data rate. Synchronised reception, using the same code at the receiver, is used for despreading and recovering the original data.
In accordance with the invention, there is provided a method of increasing capacity in a CDMA mobile communications network having a plurality of base stations associated with respective cells, comprising the step of applying gain adjustments to adjust the uplink and/or downlink gain of one or more of the base stations to achieve a generally equal load in each base station and to maximise the capacity of the network for a predetermined grade of service.
In accordance with a second aspect of the invention, there is provided a CDMA mobile communications network, comprising a plurality of base stations associated with respective cells, and gain adjustment means operable to apply gain adjustments to adjust the uplink and/or downlink gain of one or more of the base stations to achieve a generally equal load in each base station and to maximise the capacity of the network for a predetermined grade of service.
2 This system offers a cost-effective solution to increase capacity of a network without the need to add extra base stations. It allows network operators to adopt a progressive rollout. For example, in the case of third generation system UNITS, base stations may initially be placed in relatively high geographical locations to maximise coverage. These sites may then be intermixed with macrocells at lower geographical heights. In the case of operators with second generation networks, UNITS base stations may be co-located with second generation sites which can range between 200 metres above ground to 15 metres above ground. This technique allows a mix of such sites and increases the capacity of the network in io such deployments.
Embodiments of CDMA networks in accordance with the invention will now be described by way of example with reference to the drawings in which:
Figure I is a chart showing the typical noise rise with load for a CDMA base station (BS)-, Figure 2 is a schematic diagram showing the operation of four base stations of a prior art network,
Figure 3 is a chart showing the distribution of noise rise, carried traffic, cell height and failed traffic in a simulated UMTS network, the numbers on the x-axis being used as identification for the cells in the simulated network; Figure 4 is a chart showing the distribution of the F factor (intracell interference (intra+inter cell interference) for the network of Figure 3, the numbers on the xaxis being used as identification for the cells in the simulated network; 3 Figure 5 is a flow chart of steps for network planning in accordance with the invention'.
Figure 6 is a flow chart of steps showing dynamic application of the invention to a 5 network; and Figure 7 is a schematic diagram showing the operation of four base stations of a CDMA network in accordance with the invention.
io An inherent feature of CDMA is that all users have access to the whole bandwidth all of the time. Thus a frequency reuse of one is a well-known feature of CDMA based systems. This means also that CDMA is an interference-limited system. Hence any reduction in interference has a direct impact on increasing the capacity of the network.
In CDMA networks, the noise rise (defined as the total interference [intracell plus intercell interference] excluding the background noise) at a base station (13S) is a critical factor in determining how well the power control loop can perform. In practice, due to power control instability issues, the maximum noise rise at the BS is limited to what is known as an operating region. In most networks, noise rises above 6dB (which corresponds to 75% load) are not allowed at a BS. This is illustrated in Figure 1. To maintain loadings below 75%, existing BSs use a socalled 'admission control' mechanism to block new calls.
Figure 2 illustrates the problem in a prior art network. Due to the nonhomogenous nature of mobile networks, which occurs, for example, due to variations in terrain, vegetation, man-made structures such as buildings and variability of cell height, the noise rise will be non- uniform across the network.
4 For example, a geographically high cell BSA tends to suffer more from a rise in its noise than its surrounding lower cells BSB, BSC and BSD. This is due to a more favourable propagation environment, such as less obstruction by surrounding buildings. Due also to its consequently enhanced coverage area, the high cell, BSA, tends to carry a larger proportion of the local traffic than the surrounding lower cells. Furthermore the contribution of intercell interference to noise rise is also higher for these cells. Figure 3 shows the distribution of noise rise, carried traffic, cell height and failed traffic in a simulated UMTS network based on real positions of Vodafone (Registered Trade Mark)BSs in a UK city. The cells io considered are a mixture of directional and omnidirectional cells. Figure 4 shows the distribution of the F factor (intracell interference / (intra+inter cell interference) for the same network. In both Figures 3 and 4, the numbers on the x-axis are used to identify the cells in the simulated network. It will be seen that the highest BS (20021) has the highest noise rise and carries the most users. It also has one of the lowest F Factors.
The invention preferably uses estimation of the so-called 'F factor' and noise rise at the cell. The F Factor is defined as uplink intracell interference divided by total uplink interference (intracell interference plus intercell interference). It has been found that capacity can be improved by applying uplink attenuation to cells with high noise rise and low F factor. The amount of up/downlink attenuation applied to the sites can be determined in two ways.
With reference to Figure 5, a first iterative method is to use a CDMA system simulator (step 5) from which an estimate (step 6) of noise rise, F factor and carried traffic for a given network grade of service (GoS) (i. e. the percentage of successful call attempts averaged over a statistically representative number of cells) may be derived. These estimates are used with an optimisation algorithm (step 7), such as a socalled 'simulated annealing' algorithm, to choose suitable attenuation factors which will maximise carried traffic (step 8) within the network. This process may be carried out as part of the network planning process and the attenuation factors may then be applied to BSs (step 9)_ The nature of traffic used within the simulations would typically be aligned with the expected traffic mix when the network is in operation. Several simulation runs may be required depending on the variability of traffic and nature of the service mix throughout the day. This method would provide the option of adapting the network according to the time of day and hence the level and mix of traffic.
io Alternatively, the system simulation method shown in Figure 6 (or real network data where available) may be used to produce input parameters and algorithms for a real-time attenuation process which is operable to evaluate the required attenuation (step 10) to be applied in real time by the network during operation. In this method inputs such as noise rise and F factor would be deten-nined during operation. Noise rise is a measurable quantity and F factor may be estimated using the knowledge of active users and their corresponding services (such as speech, high data rate and asymmetrical packet) used in the cells. This method also provides the option of adapting the network according to the level of traffic experienced by the network throughout the day.
By introducing attenuation on up and/or downlinks and thereby reducing the coverage area of a cell which is carrying a large proportion of the traffic (see Figure 7), the amount of intercell interference is reduced and the users are redistributed so that they are registered with other surrounding cells. Thus the load is re-distributed across the cells with the aim of achieving a generally uniform load across all cells. This results in a substantial increase in the number of users supported for a given network GoS. The technique also has the added benefit of reducing the number of mobile telephones in soft handoff (i.e. those mobile telephones which are simultaneously in communication with more than one cell), 6 which in turn reduces interference on the downlink as well as reducing the traffic carried from the BS to the Radio Network Controller (RNC); the so-called "backhaul traffic".
The application of the up/downlink attenuation factors described in connection with Figure 5 may be performed in a similar way to the setting of frequencies of cells in a GSM network. It may be performed by causing the network to communicate the relevant attenuation factors to the appropriate base stations thereby to cause the relevant base station to adjust the sensitivity of its receiver io and in the case of the downlink, its transmission power. On the downlink, the control and pilot channels are preferably adjusted by the same factor such that the up and downfinks of the cells are balanced.
In summary, there has been described a technique for balancing the load across a
CDMA network and hence increase its capacity for a given network grade of service (GoS). The technique applies varying uplink and downlink attenuation factors to the cells in the network, in order to change their effective coverage area. This has the effect of changing their load (or carried traffic) and hence the level of intra and intercell interference experienced by the cells. In this way, the carried traffic is forced to be redistributed uniformly across the cells and is of particular importance in a non-homogeneous network. The level of attenuation applied can be determined using an adaptive/optimisation algorithm either dynamically in realtime at network level or as part of the radio planning process of a CDMA/UMTS network. The data used to obtain the attenuation factors may be derived using system simulation and/or real network data.
It will be appreciated by the skilled person that various other modifications and variations could be employed in relation to the embodiments described above, without departing from the scope of the present invention.
Claims (1)
- 7 CLAIMS1. A method of increasing capacity in a CDMA mobile communications network having a plurality of base stations associated with respective cells, comprising the step of applying gain adjustments to adjust the uplink and/or downlink gain of one or more of the base stations to achieve a generally equal load in each base station and to maximise the capacity of the network for a predetermined grade of service.io 2. A method according to claim 1, wherein the gain adjustments are applied in real-time during network operation.3. A method according to claim 1, wherein the gain adjustments are predetennined and substantially unchanging during network operation.4. A method according to any preceding claim, wherein the gain adjustments are calculated in dependence on the noise rise and F factor and/or the number of active users and their corresponding services, of one or more of the cells.5. A CDMA mobile communications network, comprising a plurality of base stations associated with respective cells, and gain adjustment means operable to apply gain adjustments to adjust the uplink and/or downlink gain of one or more of the base stations to achieve a generally equal load in each base station and to maximise the capacity of the network for a predetermined grade of service.6. A network according to claim 5, wherein the adjustment means is operable to perform adjustments in real-time during network operation.8 7. A network according to claim 5, wherein the adjustment means is operable to perform adjustments periodically such that the adjustments remain substantially unchanged during network operation.8. A method substantially as described herein with reference to Figures I and to 7 of the drawings.9. A CDMA mobile communications system substantially as described herein 10 with reference to Figures I and 5 to 7 of the drawings.
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9927200A GB2356527A (en) | 1999-11-17 | 1999-11-17 | Power control in a CDMA network |
GB0027578A GB2356531B (en) | 1999-11-17 | 2000-11-10 | CDMA mobile communications |
AU11659/01A AU1165901A (en) | 1999-11-17 | 2000-11-10 | Cdma mobile communication system |
PCT/GB2000/004306 WO2001037446A1 (en) | 1999-11-17 | 2000-11-10 | Cdma mobile communication system |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9927200A GB2356527A (en) | 1999-11-17 | 1999-11-17 | Power control in a CDMA network |
Publications (2)
Publication Number | Publication Date |
---|---|
GB9927200D0 GB9927200D0 (en) | 2000-01-12 |
GB2356527A true GB2356527A (en) | 2001-05-23 |
Family
ID=10864683
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB9927200A Withdrawn GB2356527A (en) | 1999-11-17 | 1999-11-17 | Power control in a CDMA network |
GB0027578A Expired - Fee Related GB2356531B (en) | 1999-11-17 | 2000-11-10 | CDMA mobile communications |
Family Applications After (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB0027578A Expired - Fee Related GB2356531B (en) | 1999-11-17 | 2000-11-10 | CDMA mobile communications |
Country Status (3)
Country | Link |
---|---|
AU (1) | AU1165901A (en) |
GB (2) | GB2356527A (en) |
WO (1) | WO2001037446A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN105848172A (en) * | 2013-12-27 | 2016-08-10 | 京信通信系统(中国)有限公司 | GSM base station amplifier signal coverage adaptation method and device |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
SE0103683D0 (en) | 2001-11-06 | 2001-11-06 | Ericsson Telefon Ab L M | Method and arrangement in a communication system |
DE10251993B4 (en) * | 2002-11-06 | 2012-09-27 | Actix Gmbh | Method and apparatus for optimizing cellular wireless communication networks |
CN100426710C (en) * | 2003-05-16 | 2008-10-15 | 华为技术有限公司 | Radio network planning method for CDMA service |
DE10328502A1 (en) * | 2003-06-25 | 2004-08-26 | Siemens Ag | Radio communications method for operating a mobile telephone system has radio coverage areas each serviced by a base station |
JP2005117357A (en) * | 2003-10-08 | 2005-04-28 | Nec Corp | Method and system for managing radio communication system, and managing apparatus |
US7949342B2 (en) | 2004-01-08 | 2011-05-24 | Interdigital Technology Corporation | Radio resource management in wireless local area networks |
US20050176419A1 (en) * | 2004-01-27 | 2005-08-11 | Triolo Anthony A. | Method and system for dynamic automatic optimization of CDMA network parameters |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0863619A1 (en) * | 1997-03-07 | 1998-09-09 | Lucent Technologies Inc. | Method for power control in wireless networks for communicating multiple information classes |
GB2340693A (en) * | 1998-04-13 | 2000-02-23 | Nec Corp | Spread spectrum communication system and base station thereof |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5276907A (en) * | 1991-01-07 | 1994-01-04 | Motorola Inc. | Method and apparatus for dynamic distribution of a communication channel load in a cellular radio communication system |
JPH06268574A (en) * | 1993-03-11 | 1994-09-22 | Hitachi Ltd | Cellular mobile communications system |
US5475870A (en) * | 1994-09-12 | 1995-12-12 | Qualcomm Incorporated | Apparatus and method for adding and removing a base station from a cellular communications system |
AU3260495A (en) * | 1995-08-31 | 1997-03-19 | Nokia Telecommunications Oy | A method of levelling a traffic load of a base station in a cellular radio system, and a cellular radio system |
JP2803716B2 (en) * | 1996-03-11 | 1998-09-24 | 日本電気株式会社 | Radio channel controller in CDMA cellular system |
KR0176103B1 (en) * | 1996-05-02 | 1999-05-15 | 양승택 | Overload cell control method in cdma mobile system |
US6148201A (en) * | 1997-08-06 | 2000-11-14 | Nortel Networks Corporation | Scalable wireless network architecture based on subscriber distribution |
-
1999
- 1999-11-17 GB GB9927200A patent/GB2356527A/en not_active Withdrawn
-
2000
- 2000-11-10 AU AU11659/01A patent/AU1165901A/en not_active Abandoned
- 2000-11-10 WO PCT/GB2000/004306 patent/WO2001037446A1/en active Application Filing
- 2000-11-10 GB GB0027578A patent/GB2356531B/en not_active Expired - Fee Related
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0863619A1 (en) * | 1997-03-07 | 1998-09-09 | Lucent Technologies Inc. | Method for power control in wireless networks for communicating multiple information classes |
GB2340693A (en) * | 1998-04-13 | 2000-02-23 | Nec Corp | Spread spectrum communication system and base station thereof |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN105848172A (en) * | 2013-12-27 | 2016-08-10 | 京信通信系统(中国)有限公司 | GSM base station amplifier signal coverage adaptation method and device |
CN105848172B (en) * | 2013-12-27 | 2019-07-02 | 京信通信系统(中国)有限公司 | A kind of adaptation method and device of the covering of GSM base discharge signal |
Also Published As
Publication number | Publication date |
---|---|
AU1165901A (en) | 2001-05-30 |
GB0027578D0 (en) | 2000-12-27 |
WO2001037446A1 (en) | 2001-05-25 |
GB9927200D0 (en) | 2000-01-12 |
GB2356531A (en) | 2001-05-23 |
GB2356531B (en) | 2003-11-05 |
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Legal Events
Date | Code | Title | Description |
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WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |