TRANSMISSION QUALITY MEASUREMENT IN A COMMUNICATION NETWORK

Abstract: A method according to the present invention for measuring the transmission quality between a base station (BS) and at least one remote station (RS) in a communication network (N) having at least one channel (c) for transferring signals between said base station (BS) and said at least one remote station (RS), comprises measuring a transmission quality (Q(c)) for signal transmissions via said at least one channel (c), and defining a transmission quality transmission quality measurement period (T(c)) for said at least one channel (c) in relation to said measured transmission quality (Q(c)). Moreover, the invention provides a system for a communication network (N) having at least one base station (BS) and at least one remote station (RS) transferring signals between each other via at least one channel (c) for carrying out the method of one of the claims 1 to 17, wherein the system comprises measuring means (4BS, 7BS; 4RS, 7RS) for measuring transmission qualities for signal transmissions via said at least channel (c), means (5BS; 5RS) for the definition of at least one transmission quality measurement period for signal transmissions between said base station (BS) and said at least one remote station (RS), and control means (1BS; 1RS) for the measurement of transmission qualities during said at least one transmission quality measurement period.

Description: I Transmission Quality Measurement in a Communication Network BACKGROUND OF THE INVENTION 1. Technical Field The present invention is related to communication networks and in particular to transmission quality measurements of communication signals between distributed components of a communication network. 2. State of the Art In distributed wireless communication systems jointly using the same frequency bands or channels, the channel actually allocated to a base station for communication with respective remote stations has to be selected. Such a channel selection can be accomplished at the instant a communication connection between a base station and a remote station is set up (e.g. DECT-systems) , centralized for all base station . covering a certain geographical area (e.g. GSM- sys erns) , or at arbitrary times (e.g. HIPERLAN/2). In the latter case, which is addressed by the present invention, the channel selection, i.e. the allocation of certain frequencies of a jointly used frequency band, is performed de-centralized and autonomously at each base station. As a result, a selected channel is not allocated to individual communication links for a base station above allocated for a base station which uses the selected channel and the frequencies contained therein, respectively, for several communication links established with this base station. Such selections and allocations of channels and frequencies, respectively, are often controlled by methods for a t t σ i o Oi Jd rr rt α H J T 0 Ω 0 rt ω Ω tP 3 i H rt O 0 0 i s: ^ CD H cn Pd Mi cn rt 3 if cn O S3* fcJ* CD H- 0 * H ø 0 l & H- 0 f- H- CD Φ H ø ro p ) 0 ^ H- 0 CD H- O H ct " Φ CD pi O 1 H- CD TJ o H CD cn i-J i CD rt 3 H- cn H Ω Pi t- 1 H- rt Ω 3 iQ O O PJ CD PJ < ω 1 3 UI CD o. CD P <! 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H- CD H- rr rt CD 3 Pi ø 0 P. • < P- i P- rt P- O J 0 rt 0 O P- CD P. P. TJ P cn 3 φ P- rr 1 0 P ) O P- Pi iQ ø J 1 0 3 ii 0 0 P- P 1 1 ii ø • < CQ 1 0 0 cn Φ Φ 1 tr 1 0 tQ cn rr PJ •<; iQ 1 o In order to reduce transmission quality measurements in a communication network, the present invention is based on the principle both to adaptively control transmission quality measurements with respect to operational condi- tions/situations in a communication network and/or to perform transmission quality measurements providing a long term transmission quality estimation for a communication networ . 5. Solution according to the Invention In particular the invention provides a method for measuring the transmission quality between a base station and at least one remote station in a communication network having at least one channel for transferring signals between the base station and the at least one remote station. The method comprises measuring a transmission quality for signal transmissions via the at least one channel, and defining a transmission quality measurement period for the at least one channel in relation to the measured transmission quality. Preferably, the measuring of the transmission quality includes measuring of a transmission quality for a channel allocated to the base station for communicating with the at least one remote station and/or measuring of a transmission quality for at least one channel available for the base station for communicating with the at least one remote station. Here, it is possible to define a transmission quality meas ¬ urement period for the allocated channel in relation to a ratio of the transmission quality value of the allocated channel and at least one of the transmission quality value of the at least one available channel. Moreover, the defining of the transmission quality measurement period include defining a transmission quality measurement period for each of the at least one available channel in relation to a ratio of the transmission quality value for the allocated channel and the transmission quality value for a respective one of the at least one available channel . As a result, the ratio for the transmission quality meas- urement period for the allocated channel can be a ratio of the transmission quality value of the allocated channel and the maximum transmission quality value of the transmission quality value for the at least one available channel. In order to select an optimal channel for the base station, the transmission quality measurement period for the allocated channel and the transmission quality measurement period for the at least one available channel are compared, whereby the allocated • channel can be replaced by allocating one of the at least one available channel having a larger transmission quality measurement period compared to the allocated channel. Further, the invention provides a method for measuring the transmission quality between a base station and at least one remote station in a communication network as defined above, wherein the method comprises determining the number of remote stations associated to the base station, and defining a transmission quality measurement period for the at least one channel in relation to the number of the remote stations for measuring the transmission quality for signal transmissions between the base station and the at least one remote stations. Since the transmission quality for remote stations being not actively communicating with the base station have a lower importance compared to the transmission quality of actively, actually communicating remote stations, it is preferred that the number of the remote stations is determined for remote stations being in communication with the base station. Moreover, a further method according to the invention for measuring the transmission quality in the above network comprises defining grouping criteria, assigning each of the at least one remote station to one of at least two remote station sets according to the grouping criteria, and defining transmission quality measurement periods for each of the remote station sets in relation to the grouping criteria. Preferably, the transmission quality measurement periods are indicative of a transmission quality measurement period for measuring the transmission quality of signal transmissions between the base station and the at least on remote station of a respective one of the remote station sets. As a result, only the transmission quality for one of the remote station sets are required to be measured during the respective one of the transmission quality measurement periods . In case no information required for the assignment of the remote stations are available, parameters of the at least one remote station associated to the base station are measured. Especially, the parameters should be in correspondence with the grouping criteria. In one embodiment, the method includes defining the grouping criteria as being indicative of at least two transmission quality ranges/groups , measuring the transmission quality for each of the at least one remote station, as- signing each of the at least one remote station to one of the remote station sets according to the respective remote station transmission quality, and defining the transmission quality measurement periods in relation to a respective one of the transmission quality ranges/groups . In a further embodiment, the method includes defining of the grouping criteria being indicative of at least two data types, determining the data type being currently communicated between the base station and each of the at least one remote station, assigning each of the at least one remote station to one of the remote station sets according to the data type communicated to/from the respective remote station, and defining the transmission quality measurement periods in relation to a respective one of the data types. Moreover, it is possible to combine the above embodiments. In one combination, for at least one of the remote station sets defined according to the transmission quality grouping criteria, at least two remote station subsets are defined according to the data type grouping criteria, and the transmission quality measurement periods for the at least two remote station subsets are defined in relation to the transmission quality ranges/groups and the data types, while transmission quality measurement periods for the remaining of the remote station sets not including remote station subsets are defined in relation to the transmission quality ranges/groups . In another combination, for at least one of the remote station sets defined according to the data type grouping criteria, at least two remote station subsets are defined according to the transmission quality grouping criteria, and the transmission quality measurement periods for the at least two remote station subsets are defined in relation to the transmission quality ranges/groups and the data types, while transmission quality measurement periods for the remaining of the remote station sets not including re- mote station subsets are defined in relation to the data types . As mentioned, the invention also provides for a method to perform transmission quality measurements for a long term estimation of the transmission quality. Here, the method for a communication network as described above comprises measuring of a transmission quality of transmission signals between a base station and at least one remote station via at least one channel allocated to the base station, defining of a first quality metric based on the signal strengths, measuring of a transmission quality of further transmission signals via the at least one channel of the base station, defining of a second quality metric based on the signal strength for the further transmission signals, and defining a transmission quality measurement period for the at least one channel in relation to the first and second quality metrics. In particular, the first quality metrics is indicative of signal interference on a respective of the transmission signals caused by the base station and/or the at least one remote station, and the second quality metric is indicative of signal interference on the further transmission signals caused by the base station and/or at least one further base station. Or more particular the first quality metric is in ¬ dicative of signal interference on a respective of the transmission signals caused by all interfering base stations and all interfering remote stations being active on the measured channel c, and the second quality metric is indicative of the maximum of the signal interference on the further transmission signals caused by at least one further interfering base station. Further, it is possible to define a third quality metric as a function of the first and second quality metrics, wherein the transmission quality measurement period is defined in relation to the third quality metric. To provide for a continuously measurement of the transmis- sion quality, a series of the first quality metric is defined based on the signal strengths being sampled over a first period terminating at a first time, and/or a series of the second quality metric is defined based on the signal strengths being sampled over a second period terminating at a second time, and/or the third quality metric is defined at a third time on the basis of the first and second quality metric series. For an embodiment of this method, the minimal second qual- ity metric of the second quality metric series is determined, whereby the third quality metric can be defined as the minimum of the first quality metric most recently defined and the minimal second quality metric . Preferably, the transmission signals are generated at the base station and/or at the at least one remote station in correspondence to communication signals being used for com ¬ munication between the base station and the at least one remote stations and/or the further transmission signals are generated at the base station and/or at the at least one further base station in correspondence to communication signals thereof, the further transmission signals having a predetermined signal level, preferable the maximum signal level to be generated at the base station and/or at the at least one further base station. For a selection of optimal channels, resulting in a further reduction of the required number of transmission quality measurements, the methods includes determining whether the third quality metric exceeds a predetermined quality level and allocating a respective channel to the base station for actual communication with the at least one remote station. Moreover, for all above methods, embodiments can be provided, wherein the transmission quality measurement periods are set to a first predetermined transmission quality meas- urement period, if the transmission quality measurement periods exceed a first predetermined transmission quality threshold, and/or the transmission quality measurement periods are set to a second predetermined transmission quality measurement period, if the transmission quality meas- urement periods are below a second predetermined transmission quality threshold, and/or the transmission quality measurement periods are defined to be within a range between a minimal transmission quality measurement period and a maximal transmission quality measurement period. Also, embodiments are considered, wherein transmission quality measurements are performed according to the transmission quality measurement periods, and the transmission quality measurements can be used to define new transmission quality measurement periods to be currently used. Referring to the method according to the invention utilizing grouping criteria, it is possible to use the transmission quality measurements according to the transmission quality measurement periods to re-assign the at least one remote station to the remote station sets and/or to the remote station subsets according to a respective one of the transmission quality measurements. Especially in the case of data type grouping criteria, it is preferred to determine data types being communicated be ¬ tween the base station and the remote stations in line with the transmission quality measurement periods for reassigning the at least one remote station to the remote station sets and/or the remote station subsets . to t . . o o σ rr 3 3 rt H rr •^ P- ø cn cn > cn rt 3 O TJ P- rt 3 rt Ω CO cn P- cr t rt Pi Φ 3 3 H ϋ O P- CD ii tr 0 i rt *< i 0 P- ro ø ø if 0 P- if P- P- 0 Pi if ii 0 ii p- Φ 0 PJ J rt o Pi J Pi ro CQ PJ cn Pi cr 0 t Ω pi iQ Φ ø 0 Pi ø CQ iQ cn Φ PJ P ii ø i ø CD O 0 cn ø cn rt ct P- cn ø if tr rt p- ø 0 Ω ø Φ ø o ro cn O P- cn P- CO rt cn cn O P- CD rr Φ n o Φ ø rr Ω cn iQ CD pi rt CO cn rt ϋ ø H rr 3 cn O 3 3 • 0 cr 0 3 P- Λ - P. 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H iQ rt r rr if p ) ø ti . • p- ø CQ cn rt ø rr Φ cn H- CD CD P ) Φ s; Φ ø rt ø rt ro P rt CQ O ϋ O 0 cn Pi cn O O 0 rt 3 Ω O P- rr tr rt if . ø Φ ø PJ Φ rr ii P- TJ i ø rr P- ii Φ Ω φ cn H H- ø O P- φ O rt cr if CD 3 CD cn P- r rr ) O 0 Pi p ) o p ) ct c ?r 0 cn ø H Φ φ O P- φ cn o Φ 0 ii H J TJ P- ø ø M. cn P ) <! 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P- rt CD O ro Φ ø 0 n o ii Pi rr 3 • < cn 3 O P- 3 r P 1 rt i CD o ø P. 3 ii 3 P- ϋ cr 0 ø ^ φ rr P- ø P- o ro rr 0 ii iQ O P- O Φ ro Ω φ O i CD P. CD ø rt J cn CQ cn O ø rr O P * rr 0 ii 0 i Φ P- Ω cn ,ζf 3 rt 0 rr O 3 cn 0 ϋ CD rr if rr cn Φ cn ro CD φ Φ rr tr 0 <! CD ro ro P- H 0 cn CD P- P- rr rt P- PJ Φ rt o Pi P- ø o rt J 0 Ω rr 0 CD O O CD if O rt ϋ ø ø iQ cr pi rr cn Φ H rt O cn : » iQ rr 0 0 cn > H 1 ø H φ ø if ro i cn rt cn 3 • < 3 ct O pi if CD 1 1 cn pi * 1 1 O I pi ii rr ro 1 ro * 1 Hi 1 1 In particular, the system can be operated with respect to the at least one channel being allocated to or available for the base station. Depending on the network in which the system according to the invention is used, the measuring means are located at the base station and/or at the at least one remote station, the transmission quality measurement period definition means are located at the base station, the control means are located at the base station and/or at the at least one remote station, and transmission and reception means are provided at the base station and at the at least one remote station for communicating the measured transmission quality. BRIEF DESCRIPTION OF THE DRAWINGS Further aspects and advantages of the invention will become apparent upon reading the following detailed description of preferred embodiments of the invention and upon reference to the drawings, in which: Fig. 1 is a schematic illustration of a communication network used for the invention, Fig. 2A illustrates a first grouping scheme according to the invention, Fig. 2B illustrates a second grouping scheme according to the invention, and Fig. 3 is a schematic illustration of a base station and a remote station according to the invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS As shown in Fig. 1, a communication network N comprises several base stations BS and several remote stations RS . The base stations BS and the remote stations RS can be any device or system which are adapted to communicate by trans- ferring data/information between each other. In particular, base stations BS include base stations of radio, mobile, cellular, public, satellite, broadcast, and computer networks, especially employed for telephone services, and any kind of device or system providing communication links be- tween remote stations. Further, remote stations RS include any kind of device or system adapted to communicate with a base station as described above and/or with each other via such a base station. Examples for remote stations RS comprise radio, mobile, cellular, stationary and satellite telephones, mobile and stationary computer systems, broadcast end user devices (e.g. a set-top-box) , end user devices for paging systems, etc.. In principle, a base station BS and remote station RS asso- ciated therewith communicate over at least one channel c. Usually, in the 'communication ' network N several channels cl, ... , c4 are provided to serve as communication links between base stations BS and remote stations RS . In terms of the invention, the channels cl, ..., c4 can be assigned to one or more base stations BS or can be just available for the base stations BS . As shown in Fig. 1, the channels cl, c2 and c3 are allocated to a base station BS X , while the channels c3 and c4 are allocated to a base sta- tion BS 2 . The base stations BS X and BS 2 utilize its assigned channels for current communication with respective remote stations RS . It is assumed that the channels c t and c 2 are available for the base station BS 2 , i.e. the base station BS 2 can utilize these channels upon assignment thereof, while current communication of the base station BS 2 is not performed via the channels cl and c2 being adjust avail- able. Comparable, the channel c 4 is available for the base station BS 1 but not used for current communication. As a result of channels being allocated to and available for different base stations BS, communication of different base stations BS, e.g. the base stations BS j^ and BS 2 , can occur over same channels as illustrated by channel c 3 of Fig. 1. Depending on the con iguration of the network N (e.g. type and number of base stations, remote stations and channels, type and amount of communicated data/information, ... ) and the current operational condition/situation of the network Ν, it is necessary to adaptively control the selection of channels c allocated for base stations BS to obtain appropriate channel transmission qualities. The selec- tion/allocation of channels for base stations BS will be described below in a greater detail . In terms of the invention, channels comprise any kind of communication links, for examples radio communication links, radio carrier, frequency bands, fixed wired communication links, communication busses, broadcast channels, satellite signal ' - beams, multiple fiber optic connections, ultrasound/ultrasonic links, etc.. In order to facilitate the understanding of the present invention, the description of preferred embodiments will refer to mobile/cellular telephone networks, wherein the network Ν is a public link mobile network, the base stations BS are service switching centers, and the remote stations RS are mobile stations (e.g. mobile/cellular telephones). As mentioned, the selection of channels to be allocated for base stations is essential for the operation of such networks to maintain a sufficient transmission quality between base stations and remote stations. The transmission quality of a channel or communication link between a base station and a remote station is assessed on the. basis of measure- ments of the signal strengths received by a base station and a remote station, respectively (e.g. RSS-measurements) . Adaptive Channel Allocation (ACA) based Transmission Oual- it Measurement Period The received signal strength (RSS) measurements to access the transmission quality between a base stations and remote stations are used to select/allocate a channel to the base station providing a desired, appropriate communication link. The results of the RSS-measurement generally fluctuate over time because of varying propagation losses (path losses) and varying transmission power of the base and re ¬ mote stations. Such fluctuations or the current traffic load can lead to a selection/allocation of channels not meeting the requirements for communication (links) between the base station and remote stations . In order to compensate for such fluctuations, an Adaptive Channel Allocation (ACA) is used which is based on two in ¬ puts, both thereof corresponding to the same considered channel. The first input is a quality measure related to the interfering RSS measured on the channel. This quality measure reflects the effect of interference on the recep- tion quality of signals communicated between the base sta ¬ tion and the remote stations using this channel for commu ¬ nication. Further, this quality measure considers interference caused by the base station and the remote stations alike. The second input is a quality measure which does not con ¬ sider interference caused by the remote stations, but con ¬ siders only interference caused by other base stations us ¬ ing the same channel . To obtain the first quality measure, a first quality metric Q s (t 1 ,c) is derived on the basis of a time series of RSS- > t t -_. <-n o > o \ o CO 3 if Ω cn cn 3 "-3 Ω cn ii rr P ) i <! P- p- cn Ω Z rt r Ω Ω P- H rt rt rt rt cn 3 3 rt p- P- pi P- rr 0 tr tr rt CD P- rr σ < Pi rr cn P- tr P- if Pi O if 0 0 . s: if if P- CD φ p j ω ( Q ø ø J 0 H- pi PJ Ω O Φ Pi • cQ i rt Φ cn 3 PJ rt CD CD ro CQ rr i rt cn if cn CQ rt P- CQ ø rt Φ ø P P- 0 P ø ø if Φ 3 0 CD 0 CD ii 0 ii cn P- P- Φ Φ H P- Ω 0 P- P- ~ H ro 3 CD i ø • cr ø 0 ii ii 0 Ω Pi p- ø 0 0 H. Pi CD 0 i PJ ro o <! cn cr Ω PJ cn CD ϋ ro Pi cn 0 CD Hi Pi • tf rt Ω ti P ø 0 rr TJ H CD P- • < — - cr rr P- cn P 1 O n rt P- CD ro Pi tr cn Φ cn P- cr ii cn P- TJ P. Q P 1 Hi ii < 0 Φ pi Ω ti ti PJ 0 ro 3 • (Q 3 • < ro o ϋ Ω - ø 0 H ro 0 P- CD Hi Ω rt PJ Ω CD rr 0 Φ ø TJ 3 P- 0 0 • tr ) ø CD ii Ω P ii rr cn P- rt 0 rt CD CD cr if ct ø PJ 0 0 o cn P ) P- • < P 1 ro pi • 0 P if rr 0 P- P- Ω 0 P- 1 i P- rr ii 0 rr cn Ω 0 cn P 1 rr rt lO 3 0 CD P ) ø O cn Φ ■ cn Ω - cn P- rt φ Φ 3 p- tr rt 0 Φ t "-3 ii ct cn ø O CO Ω CD if Ω rt P ) ø rt Ω if < ii Ω P. CD rt if cr H- cr P- cn CQ cr CO • — Ω • < 0 0 cn Ω ø P- Pi CD P- rt P- ro Pi 0 PJ 0 0 3 CD CD rt 1 P- cn z O Ω ϋ rr if pi cn cn P ) 3 cn - cn CQ cn ø rt P- PJ 0 pi 3 cn rt o P- 0 Φ Pi ct Φ ti 0 P- Ω iύ Φ P- tr rt ii Φ P- CD pi 0 cn 3 rr P- cr CD rt ii rt Φ M — CO r cn rt ro tr Ω H ø i ø rr φ o P- pi o PJ rt cn if CD tr ii •CO CO cn tr if ii tr Pi cn CO H- P. P- Ω pi o ii o t 0 cn if TJ Φ CD ro t CD 1 rr ro O φ H CD rt rt ø Φ O ø rt ii Φ 0 CQ CD Φ Φ cr ø 0 3 pi rt ro P. Φ tr ii Pi 0 tr P. φ ø CD P- P. Ω Ω i CD rt Pi P. φ rr rt 3 if 3 P. CD CD Φ P- P. cn rr cr ii 0 3 rr tr cn Hi 0 pi P- li iϋ ro p ) O 3 o Ω Φ tr PJ ^3 O Φ p- i CD Hi rr Pi Pi cn O J CO pi 0 rt O P cn Φ O ii TJ i O Pi Φ cn tr Ω pi ø i < ø Φ P- rt ø ø 0 CO CO φ ϋ CD ø H Φ rt ø φ CD 0 cn Φ ø CO Ω 3 CO ti cn CQ 1 0 rt Ω rt Pi t P- Ω Pi ϋ 3 0 (T ø Φ rr rt CD CD pi Φ - 3 3 ϋ if cn cr if O cn Ω Ω < pi tr cn CO Φ TJ CD if ii 3 J cn Ω 3 p- ro p- ro rt Pi Pi 0 ø H Φ CD pi cn rt Ml P ) r ro H- Φ rr 0 • 0 cn Φ P ) co Pi ø pi cn O Pi Ω CD P- Ω ø Φ i O H s- 0 pi Ω H- Hi 0 ro ø O to CQ 3 rt CD Φ 0 ti cn < O if ø cn rt ϋ CD o Hi CQ cn 0 P3 P Ω rt CQ P- ø ro P- Λ 0 Φ TJ Φ Hi Pi ro cn P- CD Pi ϋ pi ø o 0 cn - 0 cn Φ 0 ii ii pi O cn CO 0 cn ø Φ P. 0 P- 1 3 o •« Ω ø H ø n P- CD £1 0 Ω 0 Φ Φ cn ø rt rt PJ p- rt Ω rt 0 φ ø rt rt ø H- cQ ø P. ø O 3 3 ø ω J pi P. rr cr if φ 3 ø CO cn o P- 0 ct rt ø cn Pi cn 0 O CD O ϋ rt rt P- Φ Ω P- ■ <; CD p- rr P- rt ct rt CQ if ii Pi CD P 1 rt Φ Pi Hi 0 rt P- Pi P- P- rt ii O < rt H- ø rt tr if Φ Pi Ω P- P- P. rt Φ 0 cn 0 O • CD 3 Φ rr cn Ω tr O cn CQ if CD Pi Ω 0 0 O rr 3 >Q CQ cn CQ cn ø 0 Pi 3 if P- • Hi P 1 Φ rr O ø Λ cn P- 0 • < φ 0 0 cn O n 3 ø t, Φ CQ ti P ) φ i - 3 P- 0 3 ø P. O pi Ω Ω rt cr Ω CO Φ tr 0 Φ 0 Φ rr cn Pi < 3 rr Pi P- rr 3 rt ii tr O i PJ P- p- Pi ro P- 3 3 i if cn if cn P- < ro Hi ø cn H ΓT CD .Q Φ P- H rt cn P ) CQ rt cn H Ω o CD Φ TJ φ 0 ø Φ ii o 0 P- rr ϋ . ø rr rt rt Ω H- CD rt ø tr ø CD Pi rt Pi CD 3 rt H i ii H- . — - cr P- pi ii ør • < O φ O Φ pi Φ ii rt Φ ω P- Ω o ro CD Pi iQ Ω p- •<; ø Φ P- Φ 3 Ω ø cn P CD ro P- ø 0 P- rt < P i ii IQ ro Pi I • C ii P- Ω φ 3 3 rt rt CO Ω ø O cn ti rt li Φ Hi Φ rr φ o CD ct cn cn ii Φ 0 Φ P- pi rt O H Pi 0 rt P- Φ cn rt i rt ro H rt CD • Hi Ω 0 ^ CD CD rt 0 P CO rt 0 0 ø ro Pi ø ϋ rt 0 i o H 0 tn 0 Ω Ω cr Ω ii P- P- rt n Hi i rt rt CQ Hi ro o pi τ ii cn .3 CD 3 pi O P- Ω O i O P. P- P- P 1 rt if p- Φ .Q ii tr ø Pi P. P- < φ P- 3 CD ø 0 Ω Pi ø CO ø P- i CD ro O ø ϋ 0 CD Pi Ω i Ω P- 3 Q 0 CQ rt P. rt ti ø ø Φ J ΓT < ro 0 i pi O ø 0 CD ϋ cr ø rt cn ^ P- CD Ω 3 CD H- rt O Hi N ii rt if ro P- ø 0 H CD o Hi rt P ) P- 0 P- φ ■ s. >Q σ O if Ω 0 Φ CD ro H- CD rr Ω P- rt i Hi rt Φ \- > Ω Φ Ω ø J t 0 φ H- ti ti P. P. 0 cr P- Φ rr CD 0 P ) cr Ω if cn ) H P i ro CQ rt ro Hi cn PJ pi 0 CD 1 1 rt rt 0 Hi H- 1 Φ O 1 0 ω 3 1 Ω CD 0 rt 0 3 P- 0 • < ro P ii CD 1 In case the first quality metric Q s (t 1 ,c) is high compared to the second quality metric Q b (t 2 ,c) because interfering base stations have currently little load (i.e. a small number of active communication links supported by the base stations) , this situation is not considered to be representative for signal interference in the long term. Therefore, the long term transmission quality is estimated assuming that the base station causing the largest interference with respect to RSS transmitted the interference causing signals continuously with signal levels corresponding to the second quality metric Q b (t 2 ,c) . In order to obtain this condition, the base station (s) to be considered for RSS-measurements for the second quality metric Q b (t 2 ,c) are operated to transmit interference causing signals at the maximum signal level which is permitted to be used for any transmission of the base station (s) . To determine the long term interference for the channel c , a long term quality metric Q x (t 3 ,c) is defined as a function of the first and second quality metrics Q s (t l7 c) and Q b (t 2 ,c) . The long term quality metric Q j t^c) is defined at a time t 3 when a new value for either the first quality metric or the second quality metric is available. Assuming that the time needed to obtain (signal transmission, measurement, calculation, ...) a new value for the first and second quality metrics is rather short, the time t 3 substantially corresponds to either time t x or time t 2 . For the definition of the long term quality metric, a mini ¬ mal value of all second quality metrics corresponding to all base stations using the channel c is determined, the minimal value being denoted Q b (t 2 ,c) min , and compared with the most recent value for the first quality metric. So, the long term quality metric Q x (t 3 ,c) is defined by: Q^t^c) = g (Q,(t lf c), Q b (t a , . c) , wherein g(x,y) is a function of the two variables x and y. Here, x = QJ t^ c ) and y = Q b (t 2 ,c). In one embodiment of the Adaptive Channel Allocation (ACA) the function g is defined by: g(x,y) = min(x,y) . Therefore, the long term quality metric Q 1 (t 3 ,c) is defined as the minimum of either the current first quality metric Q 2 (t 1 ,c) or the minimal second quality metric Q b (t 2 ,c) min . As a result, the variance of the long term quality metric, i.e. the fluctuations over time, is smaller than or equal to the variance of the first quality metric. In case the first quality metric is only determined by the noise level for the channel c, the value for the first quality metric is larger than the value for the minimal second quality metric. In consequence, the value for the long term quality metric corresponds with the value for the minimal second quality metric. Further, the long term quality metric is equal to the minimal second quality metric whenever the first quality metric is dominated by transmis- sions via the channel c having a smaller transmission level and/or a larger transmission path loss compared to transmissions of the base station which determines the minimal second quality metric. In order to perform the Adaptive Channel Allocation (ACA) for a base station, the above long term quality metric is calculated for each channel available for the considered base station. On the basis of the calculated long term quality metrics, channels having a long term quality metric larger than a transmission quality threshold Q th are selected as suitable to be allocated to the considered base station. The above described procedure for channel selection/allocation (ACA) provides an increased long term transmission quality and a reduced rate of changes of chan- nels allocated to base stations. The improvements and benefits of the ACA can be utilized in any known communication network by replacing conventional channel selection/allocation procedures. Furthermore, the ACA allows to reduce the number of transmission quality measurements due to the improved reliability and the long term characteristic of the calculated transmission quality measure, i.e. the long term quality metric . On the basis of the long term quality metric, a transmission quality measurement period T(c) if defined for a channel c . Channels exhibiting a high transmission quality indicated by a high value for the long term quality metric require a smaller number of transmission quality measurements compared to channels having a smaller transmission quality, i.e. smaller values for the long term quality metric. Therefore, the transmission quality measurement period for a channel with a good transmission quality is defined to be larger in comparison to the transmission quality measurement period for a channel with a worse transmission quality. Channel based Transmission Quality Measurement Period This embodiment is based on the approach to adaptively control transmission quality measurement periods separately for each channel c l7 ... , c n in dependence on the current accessed respective transmission quality Q (cA , ■ • ■ ■ Q (cJ ■ The transmission quality Q(c) for a channel c is calculated on the basis of up-link and down-link measurements for the channel c, for example RSS-measurements .._ The measurement period T(c) indicative of the time interval between two successive transmission quality measurements for channel c depends not only on the quality Q(c) of each channel c but is also selected differently for channels allocated and used by a base station and a channels available for other base station but not used by the same. Further, it is assumed that a base station BS uses a channel c 0 allocated therewith, while channels c ul , ... , c un are available for but not used by the base station BS . In general, the transmission quality measurement period T(c 0 ) for the used channel c 0 should be the shorter the worse the quality Q(c 0 ) of the used channel c 0 is compared to the maximal value of the transmission quality values Q(c ul ), ..., Q(c un ) for the unused channels c ul , ..., c un . Therefore, the transmission quality measurement period T(c 0 ) for the used channel c 0 is given by: T(c 0 ) = A • Q(c 0 )/max(Q(c ul , ..., Q(c ), wherein A is a predetermined value previously defined with respect to the technical characteristics of the considered network. Further, the transmission quality measurement period T(c ul ), ... , T(c un ) for unused channels c ul , ... , c un should be selected shorter the better the quality of the respective unused channel is compared to the quality Q(c 0 ) of the currently used channel c 0 . So, the transmission quality meas- urement periods T(c u ) for an unused channel c u is given by: T(c u ) = B • Q(c 0 )/Q(c u ) , wherein B is a predetermined value previously defined in relation to the technical characteristics of the considered network. As a result of this definition of transmission quality measurement periods is that unused channels c u are more often measured the closer the transmission quality Q(c thereof is to the transmission quality Q(c 0 ) of the cur- rently used channel c 0 . This definition considers the fact that an unused channel c u becomes a candidate for a channel selection/allocation for the base station BS upon exhibiting an improved unused channel quality Q(c . When the currently used channel c 0 has a high transmission quality Q(c 0 ) compared to the transmission quality Q(c u ) of unused channels c u there is no need for a channel reselec- tion/reallocation. Therefore, the transmission quality measurement period T(c 0 ) for the used channel c 0 is defined to be longer. This is a special importance for small net- works, especially for single cell networks, in which the number of available channels with excellent transmission quality, i.e. channels with substantially no interference, is higher than the number of currently used channels. Base Station related Transmission Ouality Measurement Periods In this embodiment, transmission quality measurement periods are adaptively controlled for each base station depend- ing on the number of remote station associated with a single base station. Here, the number N of remote stations RS associated with a base station and available for transmis ¬ sion quality measurements is determined, and a transmission quality measurement period T(c) for a channel c allocated to the base station BS is defined depending on the number N of remote stations RS . 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H- 1 cn 1 Hi 1 1 1 to to __. O o o For assigning the remote s tations RS to a certain remote station set S ( i , c ) , dif ferent solutions are possible , namely a strictly ordered assignment or a threshold based assignment . For the strictly ordered assignment, the first N max remote stations RS having the lowest transmission quality values q(m,c) are assigned to a first remote station set S(l,c). The next N maκ remote stations RS with the next low transmis- sion quality values q(m,c) are assigned to a second remote station set S(2,c) and so forth. The last remote station set S(i max ,c) contains the last remaining remote stations RS having the highest transmission quality values q(m,c). As a result of the strictly ordered assignment, all remote sta- tion sets S(i,c) contain the same number N max of remote stations RS, while only the last remote station set S(i max ,c) can contain less than N raax remote stations RS . In Fig. 2A a strictly ordered assignment of remote stations RS is illustrated, ' wherein the maximal number Nmax of remote stations RS is three and the number i of remote station sets S(i,c) is three . For the threshold based assignment, the remote station sets S(i,c) are defined to cover a certain transmission quality range, each thereof between an upper and a lower transmission quality threshold q t . As shown in Fig. 2B, the remote station set S(l,c) covers the frequency range between the lower threshold q x and the upper threshold q 2 , the remote station set S(2,c) covers the frequency range between the lower threshold q, and the upper threshold q 3 , and so forth. The thresholds q t can be fixed parameters or can be modified during the operation of a respective communication network in relation to desired and/or actual operation conditions thereof. The thresholds q t do not have to be uni- formly distributed over the considered transmission quality range . H- 0 ) n 0 3 ø 0 P- Ω Pi rr H- 0 ø ≥! CD rt -3 0 ϋ tf suits of the remote station RS to the base station BS, e.g. by means of the sender means 3RS. The base station BS and the remote station RS shown in Fig. 3 are adapted to implement one or several of the above described methods for defining transmission quality measurement periods. In particular, it is possible that the base station BS utilizes a different method compared to the method utilized by the remote station RS . Further, it is contemplated that both the base station BS and the remote station RS utilize at least two of the above described methods in combination, wherein such a combination includes a subsequently application of selected methods and application of methods at the same time.

Claims: CLAIMS 1. A method for measuring the transmission quality between a base station (BS) and at least one remote station (RS) in a communication network (N) having at least one channel (c) for transferring signals between said base station (BS) and said at least one remote station (RS) , said method comprising: measuring a transmission quality (Q(c)) for signal transmissions via said at least one channel (c) , and defining a transmission quality measurement period (T(c)) for said at least one channel (c) in relation to said measured transmission quality (Q(c)) . 2. The method of claim 1, wherein said measuring of said transmission quality (Q(c)) includes: measuring of a transmission quality (Q(c 0 )) for a channel (c 0 ) allocated to said base station (BS) for communicating with said at least one remote station (RS) and/or - measuring of a transmission quality (Q(c ul ), ..., Q(c un )) for at least one channel (c ul , ..., c un ) available for said base station (BS) for communicating with said at least one remote station (RS) . 3. The method of claim 2, wherein said defining of said transmission quality measurement period (T(c)) includes: defining a transmission quality measurement period (T(c 0 ) for said allocated channel (c 0 ) in relation to a ratio (R 0 ) of said transmission quality (Q(c 0 )) of said allo- cated channel (c 0 ) and said transmission quality (Q(c ul ) ..., (Q(c url )) of said at least one available channel (c ul , ... , c un ) , and/or defining a transmission quality measurement period (T(c ul ), ..., (T(c un )) for each of said at least one avail- able channel (c ul , ..., c un ) in relation to a ratio of said transmission quality (Q(c 0 )) for said allocated channel (c 0 ) and the transmission quality (Q(c ul ), ...., (Q(c ) for a re- spective one of said at least one available channel (c ul , • • • , . 4. The method of claim 3, wherein said ratio for said transmission quality measurement period (T(c 0 )) for said allocated channel (c 0 ) is a ratio of said transmission quality (Q(C 0 )) of said allocated channel (c 0 ) and the maximum transmission quality of said transmis- sion quality (Q(C ul ), ..., Q(C un )) for said at least one available channel (c ul , ... , c un ) . 5. A method for measuring the transmission quality between a base station (BS) and at least one remote station (RS) in a communication network (N) having at least one channel (c) for transferring signals between said base station (BS) and said at least one remote station (RS) , said method comprising: determining the number of remote stations (RS) associ- ated to said base station (BS) , and defining a transmission quality measurement period (T(c)) for said at least one channel (c) in relation to said number of said remote stations (RS) for measuring the transmission quality for signal transmissions between said base station (BS) and said at least one remote stations (RS) . 6. A method for measuring the transmission quality between a base station (BS) and at least one remote station (RS) in a communication network (N) having at least one channel (c) for transferring signals between said base station (BS) and said at least one remote station (RS) , said method comprising: defining grouping criteria, - assigning each of said at least one remote station (RS) to one of at least two remote station sets according to said grouping criteria, and defining transmission quality measurement periods (T sl , ... , T sn ) for each of said remote station sets in relation to said grouping criteria. 7. The method of claim 6, including: defining said grouping criteria as being indicative of at least two transmission quality ranges/groups, measuring the transmission quality for each of said at least one remote station (RS) , - assigning each of said at least one remote station (RS) to one of said remote station sets according to the respective remote station transmission quality, and defining said transmission quality measurement periods (T sl , ... , T sn ) in relation to a respective one of said transmission quality ranges/groups . 8. The method of claim 6, including the steps of: defining of said grouping criteria being indicative of at least two data types, - determining the data type being currently communicated between said base station (BS) and each of said at least one remote station (RS) , assigning each of said at least one remote station (RS) to one of said remote station sets according to the data type communicated to/from the respective remote station (RS) , and defining the transmission quality measurement periods (T sl , ... , T sn ) in relation to a respective one of said data types . 9. A method for measuring the transmission quality between a base station (BS) and at least one remote station (RS) in a communication network (N) having at least one channel (c) for transferring signals between said base sta- tion (BS) and said at least one remote station (RS) , said method comprising: measuring a transmission quality of transmission sig- nals between a base station (BS) and at least one remote station (RS) via at least one channel (c) allocated to said base station (BS) , - defining of a first quality metric (Q s (t x ,c)) based on said signal strengths, measuring a transmission quality of further transmission signals via said at least one channel (c) of said base station (BS) , - defining of a second quality metric (Q b (t 2 ,c)) based on said signal strength for said further transmission signals, and defining a transmission quality measurement period (T(c)) for said at least one channel (c) in relation to said first and second quality metrics (Q s (t 1 ,c), Q b (t 2 ,c)). 10. The method of claim 9, wherein - said first quality metrics (Q s , (t 1 ,c)) being indicative of signal interference on a respective of said transmission signals caused by said base station (BS) and/or said at least one remote station (RS) , and - each of said second quality metrics (Q b (t 2 ,c,b)) being indicative of signal interference on a respective one of said further transmission signals caused by said at least one further base station (BS) . 11. The method of claim 9 or 10, including: definition of a third quality metric (Q^t^c)) as a function of said first and second quality metrics (Q.ft^c), Q b (t 2 ,c,b) ) , and defining said transmission quality measurement period (T(c)) in relation to said third quality metric (Q a (t 3 ,c)) . 12. A method of one claim 11, including: - determining a minimal second quality metric (Q b (t 2 ,c) min ) of a series of said second quality metric (Q b (t2,c)), and defining said third quality metric (Q.t3,c)) as the minimum of said first quality metric (Q^t^c)) most recently defined and said minimal second quality metric (Q b (t 2 ,c) min ). 13. The method of claim 11 or 12, including: determining whether the third quality metric (Q 3 (t 3 ,c)) exceeds a predetermined transmission quality level (Q eh ) , and - allocating a respective channel to said base station (BS) for actual communication with said at least one remote station (RS) . 14. The method of one of the claims 1 to 13, wherein - said transmission quality measurement periods are set to a first predetermined transmission quality measurement period (TJ , if said transmission quality measurement periods exceed a first predetermined transmission quality threshold (QJ , and/or - said transmission quality measurement periods are set to a second predetermined transmission quality measurement period (TJ , if said transmission quality measurement periods are below a second predetermined transmission quality threshold (QJ , and/or- - said transmission quality measurement periods (T) are defined to be within a range between a minimal transmission quality measurement period (T min ) and a maximal transmission quality measurement period . 15. The method of one of the claims 1 to 14, wherein transmission quality measurements are performed according to said transmission quality measurement periods (T) , and said transmission quality measurements are used - - for defining new transmission quality measurement pe ¬ riods to be currently used, and/or - - to re-assign said at least one remote station (RS) to said remote station sets and/or to said remote station subsets . 16. The method of one of the claims 1 to 15, wherein said measuring of said transmission quality includes: - determining of signal strengths and/or numbers of transmission errors for signal transmissions between said base station (BS) and said at least one remote station (RS) . 17. A method for measuring the transmission quality between a base station (BS) and at least one remote station (RS) in a communication network (N) having at least one channel (c) for transferring signals between said base sta- tion (BS) and said at least one remote station (RS) , said method comprising: - defining transmission quality measurement periods by a method resulting from a combination of at least two of the methods according to claims 1, 5, 6, and 9. 18. A system for a communication network (N) having at least one base station (BS) and at least one remote station (RS) transferring signals between each other via at least one channel (c)for carrying out the method of one of the claims 1 to 17, comprising: measuring means (4BS, 7BS; 4RS, 7RS) for measuring the transmission quality for signal transmissions via said at least channel (c) , means (5BS; 5RS) for the definition of at least one transmission quality measurement period for signal transmissions between said base station (BS) and said at least one remote station (RS) , and control means (IBS; IRS) for the measurement of the transmission quality according to said at least one trans- mission quality measurement period. 19. The system of claim 18, said system being adapted to be operated with respect to said at least one channel (c) being allocated to or available for said base station (BS) . 20. The system of claim 19 or 20, wherein said measuring means (4BS, 7BS; 4RS, 7RS) are located at said base station (BS) and/or at said at least one remote station (RS) , said transmission quality measurement period defini- tion means (5BS; 5RS) are located at said base station (BS) , said control means (IBS; IRS) are located at said base station (BS) and/or at said at least one remote station (RS) , and - transmission and reception means (2BS,3BS ; 2RS, 3RS) are provided at said base station (BS) and at said at least one remote station (RS) for communicating the measured transmission quality.

Inventors: HUSCHKE JOERG, TORSNER JOHAN, ZIMMERMANN GERD, HUSCHKE, JOERG, TORSNER, JOHAN, ZIMMERMANN, GERD
Applicants: ERICSSON TELEFON AB L M, TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
Application year: 2001
Main classification: H04B17
IPC codes: H04B17