PTO O7-4791
`
`CC=DE
`DATE=l9990729
`KIND=AN
`PN=l9800953
`
`S’e'e' Pm?“ 3- (fuarkw
`
`Procedure and Radio Communication System to Allocate the
`Radio Resources of a Radio Interface
`
`_Gerhard Ritter
`
`UNITED STATES PATENT AND TRADEMARK OFFICE
`
`WASHINGTON, DC
`
`June 2007
`
`Translated by:
`
`“SCHREIBER TRANSLATIONS INC."
`
`SPRINT 1 104
`
`
`
`CC=DE
`DATE=l9990729
`KIND=AN
`PN=l9800953
`
`S’e'e' Pm?“ 3- (fuarkw
`
`Procedure and Radio Communication System to Allocate the
`Radio Resources of a Radio Interface
`
`_Gerhard Ritter
`
`UNITED STATES PATENT AND TRADEMARK OFFICE
`
`WASHINGTON, DC
`
`June 2007
`
`Translated by:
`
`“SCHREIBER TRANSLATIONS INC."
`
`SPRINT 1 104
`
`
`
`PUBLICATION COUNTRY
`
`(10): DE
`
`DOCUMENT NUMBER
`
`(11):
`
`19800953
`
`DOCUMENT KIND
`
`(12);
`
`PS
`
`PUBLICATION DATE
`
`(43):
`
`19990729
`
`APPLICATION NUMBER
`
`(21):
`
`19800953.4—35
`
`APPLICATION DATE
`
`(22):
`
`19980113
`
`INTERNATIONAL CLASSIFICATION (51):
`
`H043 7/005, HO4B 7/204,
`
`PRIORITY COUNTRY
`
`PRIORITY NUMBER
`
`PRIORITY DATE
`
`INvENTOR(s)
`
`PATENT HOLDER
`
`H04B 7/26, H04J 13/02, HO4Q
`
`7/38,
`
`H04L 27/00
`
`(33):
`
`(31):
`
`(32):
`
`(72):
`
`Gerhard Ritter
`
`(73):
`
`Siemens Inc.
`
`DESIGNATED CONTRACTING STATES (81):
`
`TITLE
`
`(54):
`
`Procedure and Radio
`
`Communication System to
`
`Allocate the Radio Resources
`
`of a Radio Interface
`
`FOREIGN TITLE
`
`[54a]: Verfahren und Funk-
`
`Kommunikationssystem zur
`
`Zuteilung Von Funkressourcen
`
`einer Funkschnittstelle
`
`
`
`Description
`
`/1
`
`The invention involves a procedure to allocate the
`
`radio resources of a radio interface of a radio
`
`communications system as well as a corresponding radio
`
`communication system.
`
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`
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`
`As is known radio communication systems manifest a _
`
`radio interface across which data symbols can be
`
`transmitted between a fixed base station and usually
`
`several mobile station in a radio coverage area — e.g. a
`
`radio cell.
`
`In the process multiplex access procedures are
`
`
`
`used,
`
`in order to be able to effectively use the radio
`
`resources of the radio interface; A classic multiple access
`
`procedure is the time multiplex (TDMA, Time Division
`
`Multiple Access)
`
`in which the data symbols are contained in
`
`bursts in a time slot. Another multiplex access procedure
`
`is the code multiplex (CDMA, Code Division Multiple Access)
`
`in which each data symbol is splayed with several code
`
`symbols on a certain bandwidth.
`
`In addition,
`
`there is the OFDMA multi—carrier
`
`procedure (Orthogonal Frequency Division Multiple Access)
`
`which uses the OFDM principle to transmit the data symbols
`
`according to Chapter 15.3.2 of “Information Transmission”,
`
`K. D. Kammeyer, Teubner Publishers, Stuttgart,
`
`2nd Edition,
`
`1996. Almost rectangular-shaped,
`
`transmission and reception
`
`Afilter impulse, responses enable a FFT (Fast Fourier
`
`Transformation) or an IFFT (Inverse Fast Fourier
`
`‘ Transformation) based signal processing in the transmitter
`
`and receiver which allows for high data rates with
`
`relatively low complexity. It is also advantageous,
`
`that
`
`narrow band sub-carriers (OFDMA carriers) which, for
`r—’p:
`
`example, can only be separated from each other by a few
`
`kilohertz enabl
`a fine granularity of the data rates
`~—*
`
`depending on the actual application. Thus a number of sub—
`
`
`carriers and also a segment of a frequency spectrum can be
`
`
`
`allocated for the communication link between the base
`
`station and the mobile station.
`
`From German Patent DE 4441323A1 a procedure is known
`
`to transmit OFDM signals in a mobile communication system
`
`in which for high transmission rates dynamically reduced
`OFDM signals can be amplified by a transmission amplifier
`
`within a basically linear amplification range.
`
`The invention has the goal of providing an improved
`
`procedure and radio communication system for allocating
`
`radio resources, when using a OFDMA multi-carrier
`
`procedure.
`
`This goal.is achieved in the invention by the
`
`procedure with the characteristics of Patent Claim 1 and by
`
`a radio communication system with the characteristics of
`
`Patent Claim 12. Further variations of the inventions can
`
`be taken from the sub—claims.
`
`[1( The procedure of the invention begins with the OFDMA
`
`multi-carrier procedure and the use of a number of sub-
`
`carriers which are assigned for the communication link
`
`between the base station and the mobile stations and
`
`includes the following steps:
`
`— Measure the quality of various segments of the
`
`frequency spectrum through each mobile station,
`
`
`
`— Determine at least one suitable segment preferred
`
`for its own communication link through each mobile
`
`station and the transmission of appropriate
`
`information to the base station,
`
`fig’
`
`— Evaluate the information received from the mobile
`stations through the base station and allocate a/2
`
`segment for the respective communication link to each
`
`mobile station depending on the evaluation,
`
`— Transmit
`
`information across the allocated segment to
`
`each mobile station through the base station.
`
`‘1
`
`The radio communication system of the invention also
`
`begins with the OFDMA multi-carrier procedure and the use
`
`of a number of sub—carriers which are allocated for the
`
`communication link between the base station and the mobile
`
`station and includes the following means:
`
`/6
`- Control means in each mobile station to measure the
`."
`
`quality of various segments of the frequency spectrum
`
`
`and to determine at least a suitable segment preferred
`
`
`for its own communication link,
`
`1|
`
`- Control means in each mobile station to transmit
`
`:;d;___appropriate information to the base station,
`
`— Control means in each base station to evaluate the
`
`information received from the mobile stations and to
`
`
`
`allocate a segment for the respective communication
`
`link to each mobile station depending on the
`
`evaluation, as well as
`
`- Transmission means in each base station to transmit
`
`information across the assigned segment to each mobile
`
`station.
`
`By means of the allocation system described the-
`
`advantages of the OFDMA multi-carrier procedure can be used
`
`
`
`
`
`
` Ctgghaand possibly optimal frequency resources can be provided :[f
`
`for all communication links operated by a base station with
`
`
`the help of a flexible allocation of several sub-carriers
`
`
`and a thereby defined segment of a frequency spectrum. In
`
`
`the quality of the actual communication link
`the process,
`y———:¢
`
`plays a decisive role with respect to the frequency
`
`
`situation which according to the procedure of the invention
`
`can be individually changed after the determination of the
`‘
`.
`
`best suitable segments in each mobile station overseen by a
`
`
`base station and can thereby be improved.
`
`{Q
`
`Another important advantage consists of the fact,
`that
`by means of the invention the interferences, especially the
`critical inter—cell interference in the radio communication
`
`‘.
`
`systems and the inter—symbol interferences, are considered
`
`2fic*1VLQ&fl
`2f.§ fl
`
`and compensated for.
`
`
`
`
`
`By means of the procedure of the invention and the
`
`radio communication system a cost effective and more
`
`effective — primarily for higher frequencies in the MHz
`
`range — allocation of frequency resources is obtained using
`
`
`
`the OFDMA multi—carrier procedure, as compared to a
`
`wideband communication. The improved OFDMA multi-carrier
`
`procedure can be combined with other multiplex access
`
`procedures which transmit data symbols of a finite duration
`
`jiL/,_in time slot into a more effective radio system. Thus the
`
`improved OFDMA multi—carrier procedure according to an
`__i___________________________________
`
`5,»
`«
`especially preferred variant can be integrated into a
`.. -———-
`
`TDMS/CDMh radio system which for applications with less
`
`power requirements — e.g., micro-cell systems — or for TDD
`
`applications (Time Division Duplex) or for applications
`
`with higher data rates — e.g., for indoor systems, wireless
`
`systems or for applications with low movement speeds acts
`
`in an especially advantageous manner.
`
`The flexibility of the procedure of the invention can
`
`be especially used in an advantageous manner, if segments
`
`of the frequency spectrum are allocated to the mobile
`
`/3
`
`stations by the base station whose bandwidths vary or a /2
`
`different number of time slots for the transmission of data
`
`symbols are assigned to the allocated segments. Thus the
`
`best suited segments for communication can be determined at
`
`
`
`any time for individual communications links which differ
`
`from each other and they can be changed as needed.
`
`According to another version of the invention a
`
`priority list is sent from the mobile station to the base
`
`9/
`
`station which contains information about
`
`the segment best
`’_______,_..j—i‘
`
`suited for its communication link as well as other suitable
`;
`
`segments preferred for its own communication link. As a
`
`
`result,
`
`the base station receives knowledge from the
`
`incoming lists of the desires of the mobile station with
`
`respect to the best suited segment for it and can make
`
`appropriate new assignments of the segments of the
`
`frequency spectrum for all mobile stations which are better
`
`adapted to their transmitted needs.
`
`It has proven useful,
`
`that the number of assigned sub-
`
`carriers in a time slot be set variably by the base station
`
`for each mobile station,
`
`in order to not only change the
`
`segments when needed but to also be able to change their
`
`bandwidth.
`
`Another advantageous model of the invention to measure
`
`the quality of segments of the frequency spectrum
`
`envisions,
`
`that the mobile station receives all sub-
`
`carriers in the time slot allocated to it, checks for each
`‘
`
`sub—carrier; whether an amplitude modulation of the data
`'
`
`symbols transmitted in the time slot is present, and forms
`
`
`
`
`
`an average value from the results of the test for all sub-
`
`carriers belonging to the respective segment. The advantage
`.——-—-—:——-"""‘“'.-—————-'—"*‘z—""“**‘*
`
`lies in the two-step procedure in which initially the
`
`quality is determined for the individual sub—carriers and
`
`then the quality of the sub-carriers can be ascertained to
`
`determine the quality of the segment that was examined in
`
`particular.
`
`An especially simple method to measure quality
`
`consists of so determining the relative deviations of the
`
`amplitudes of the data symbols,
`
`that the absolute amplitude
`
`difference from data symbol to data symbol is added up and
`
`the addition result is normalized with the average
`
`amplitude of all data symbols transmitted on a given sub-
`
`carrier.
`
`According to another variant of the invention the
`
`radio communication system manifests a mobile station with
`
`a control means to measure the quality of various segments
`
`of the frequency spectrum and to determine at least one
`
`suitable segment preferred for its communication link, as
`
`well as a transmission means to transmit suitable
`
`appropriate information to the base station.
`
`In another variation of the invention the radio
`
`communication device manifests a device which in
`
`alternative configurations is characterized as a part of
`
`10
`
`
`
`the base station or the base station control with a control
`
`means to evaluate the information received by the mobile
`
`stations and to allocate to each mobile station a segment
`
`for the communication link depending on the evaluation, as
`
`well as a transmission means to transmit information across
`
`the allocated segment to each mobile station.
`
`In the following section the device of the invention
`
`will be described using execution models and references to
`
`the drawings.
`
`lshown thereby
`
`Figure 1 is a block diagram of a mobile radio system
`
`with several mobile stations overseen by a base station,/4
`
`Figure 2 is a schematic depiction of a structure of a
`
`radio block with data symbols in a time slot as well as the
`
`OFDMA sub—carrier to form the segments of a frequency
`
`spectrum,
`
`Figure 3 is an information flow to allocate frequency
`
`resources to the mobile stations,
`
`.Figure 4 is a schematic depiction of the amplitude
`
`modulation of the transmitted data symbols on a OFDMA sub-
`
`carrier to measure the quality of the segments,
`
`Figure 5 is a block diagram of a mobile station, and
`
`10
`
`11
`
`
`
`Figure 6 is a block diagram of a base station / base
`
`station control.
`
`The radio communication system shown in Figure 1
`
`corresponds in its structure to a known mobile radio
`
`system;
`
`the network devices of a mobile radio net,
`
`like
`
`e.g.,
`
`the mobile relay positions, MSC, which are networked
`
`to each other provide the access to a fixed network, PSTN,
`
`and manifest base stations, BS, connected to a base station
`
`control, BSC, and the base station controls, BSC, connected
`
`with the mobile relay positions, MSC. Such a base station,’
`
`BS,
`
`is a fixed radio station which establishes and
`
`maintains communication links to the mobile stations, MS,
`
`via a radio interface. Shown in Figure l,
`
`for example, are
`
`three radio connections between the mobile stations, MS,
`
`and a base station, BS. An Operation and Maintenance
`
`Center, OMC, performs control and maintenance functions for
`
`the mobile radio system or for parts of it. The Operation
`
`and Maintenance Center, OMC, and the base station control,
`
`BSC, usually perform the functions of regulating and
`
`adapting the allocation of radio resources within the radio
`
`cells of the base station, BS. The functionality of the
`
`radio communication system can also be conveyed to another
`
`radio communication system, if necessary, even with a fixed
`
`H
`
`12
`
`
`
`mobile station, MS. The procedure of the invention can even
`
`be used in such a radio communication system.
`
`The communication links between the base station, BS,
`
`and the mobile stations, MS, are subject to a multiple path
`
`expansion which can also be caused by reflections,
`
`for
`
`example, off buildings or vegetation,
`
`in addition to a
`
`direct expansion path. If one assumes a movement of the
`
`mobile stations, MS,
`
`then the multiple path expansion
`
`together with other interference results in the signal
`
`components of the various expansion paths of a
`
`participant's signal being overlaid in time at the
`
`that a
`receiving base station, BS. It will also be assumed,
`<7”‘-———-—-—————-""-——*“““‘——-~—~.__
`
`OFDMA multi—carrier procedure is used to transmit data
`
`
`number of sub—carriers and thus a segment of a frequency
`
`
`spectrum for the communication link between the base
`
`station, BS, and a mobile_station, MS.
`
`‘yes
`
`‘ According to the device of the invention every'mobile
`
`station, MS, measures the quality of various segments of
`
`the frequency spectrum, whereby it receives all sub-
`
`carriers in the time slot assigned to it, checks the
`
`quality of each individual sub—carrier and then determines
`
`the quality of the sub—carriers. Then each mobile station
`
`determines at least a suitable segment preferred for its
`
`12
`
`13
`
`
`
`own communication link and transmits appropriate
`
`information to the base station, BS.
`
`In this example the
`
`first mobile station determines a segment, Sx, with sub-
`
`carriers oc0O m‘Oc40 as the best suitable segment for it.
`
`In addition, it determines the segments, Sy, Sz as
`
`additional suitable segments preferred for its own
`
`communication link. Information about segments Sx, Sy, Sz
`
`/5
`
`is entered on a priority list, PL1, numbered according /3
`
`to their suitability for the communication link and sent to
`
`the base station, BS.
`
`.In a similar manner,
`
`the second mobile station
`
`determines a segment, Sa, with sub—carriers oc41 m oc60 as
`
`the suitable segment best for it.
`
`In addition, it
`
`determines segments, Sb, Sc, as additional suitable
`
`segments preferred for its own communication link.
`
`Information about segments Sa, Sb, Sc is entered on a
`
`priority list, PL2, numbered according to their suitability
`
`for the communication link and likewise is sent to the base
`
`station, BS.
`
`Also the third mobile station, MS, overseen by the
`
`base station, BS, determines a segment, Sm, with sub-
`
`carriers, cc61 m ccloo and the best suitable segment for
`
`its communication link.
`
`In addition, it provides in a
`
`B
`
`14
`
`
`
`priority list, PL3, segments, Sn, So, as additional
`
`suitable segments preferred for its own communications
`
`link. The information about these three segments, Sm, Sn,
`
`So, which are numbered in the priority list, PL3, according
`
`to their suitability for the communication link, are also
`
`then sent to the base station, BS. It can be seen from the
`
`examples,
`
`that the number of sub-carriers co m
`
`and thus
`
`the bandwidth of segments S m can be variably selected.
`
`The base station, BS, evaluates all information
`
`received from the mobile stations, MS, and assigns each
`
`mobile station a segment for the respective communication
`
`link depending on the evaluation. The base station sends
`
`the mobile station information about the assigned segment.
`
`It is assumed in this example,
`
`that each mobile station,
`
`MS, can be assigned the best suitable segment desired by
`
`it. That also depends on the transmission conditions and/or
`
`the capacity utilization of the radio cell overseen by the
`
`base station, BS, according to presets of the Operation and
`
`Maintenance Center, OMC, or the base station control, BSC,
`
`for radio resource management. Thus the first mobile
`
`station, MS, receives segment Sx,
`
`the second mobile
`
`station, MS,
`
`the segment Sa, and the third mobile station,
`
`MS,
`
`the segment Sm, accordingly with the appropriate OFDMA
`
`sub—carriers, co m, assigned by the base station, BS. A
`
`M
`
`15
`
`
`
`different number of time slots to transmit data symbols in
`
`the allocated segments can also be assigned to the
`
`individual mobile stations, MS.
`
`The flexibility of the procedure of the invention is
`
`used in an especially advantageous manner, when segments of
`
`the frequency spectrum are allocated to the mobile
`
`stations, MS, by the base station, BS, whose bandwidths are
`
`different or there are different numbers of time slots for
`
`the transmission of data symbols in the assigned segments.
`
`Thus the best suited segments for communications are
`
`determined at any time for individual communications links
`
`which differ from each other and can be changed, if needed.
`
`shown schematically in Figure 2 is the structure of a
`
`radio block with data symbols in a time slot, as well as
`5.-j_——--j‘
`
`the OFDMA sub-carriers to form the segments according to
`jj——{%—
`
`the examples in Figure 1. There are thus available, for
`e;;mplei—s;veral_hundred-sub-carriers, oc,
`— with a
`
`separation of several kilohertz between two adjacent
`
`carriers — in the radio cell of Figure 1 with three mobile
`
`stations, MS,
`
`linked to the base station, BS. Sub-carriers
`
`ocoo N oc40 define segment Sx, sub-carriers oc4l M oc60
`
`idefine segment Sa, and sub-carriers oc61 W ocloo define
`
`segment Sm, appropriately distributed by the base station
`
`to the mobile stations. other sub-carriers oclol W ocXYZ/6
`
`U
`
`16
`
`
`
`are available in the entire frequency band usable for the
`
`net operator which also contains the segments Sy, Sz and
`
`Sb, Sc, and Sn, So with a number of sub—carriers also
`
`categorized as suitable by the mobile stations. According
`
`to Figure 2 an identical bandwidth is assumed for segments
`
`Sx, Sm _That, however,
`
`is no prerequisite for a radio
`
`communication system in the sense of the invention.
`
`The radio block shown as an example in Figure 2 is
`
`transmitted in a time slot of a TDMA frame structure.
`
`Provided in each frame is at least one time slot for one or
`
`more participant signals. A preset number of sub—carriers
`
`is used by the base station in each time slot on which a
`
`preset number of data symbols is transmitted. In addition,
`
`for each mobile station the number of assigned sub—carriers
`
`in a time slot can be variably adjusted by the base
`
`station.
`
`The duration of the radio block is designated with
`
`Tbu. The radio block includes two blocks each with N data
`
`symbols, d, whereby each block as a length of TbL both
`
`blocks are separated by a training sequence,
`
`tseq, with a
`
`duration of TM“. The end of the radio block forms a
`
`protective time, T; which is supposed to compensate for the
`
`running time variations because of the different distances
`
`of the mobile stations, MS,
`
`from the base station, BS. Also
`
`16
`
`17
`
`
`
`shown in Figure 2 is how an individual data symbol, d, can
`
`be transmitted in a pure CDMA procedure — shown on left —
`
`or in a pure multi-carrier procedure — shown on the right.
`
`In the CDMA procedure each data symbol, d,
`
`is splayed with
`
`Q code symbols on the broadband, Bu_
`
`In the multi—carrier
`
`procedure each data symbol, d,
`is modulated on the Q
`carrier, whereby the total of the broadbands of the carrier
`
`gives the broadband, Bu
`
`In both cases the duration the
`
`transmission of the data symbol provides the symbol
`
`duration, T3 Thus the radio communication system is
`
`constructed as a TDMA/CDMA mobile radio system in which the
`
`data symbols, d, of several communication links can be
`
`transmitted in the frequency channels formed by the time
`
`slots, whereby the information from various links can be
`
`differentiated according to a fine structure individual for
`
`each link, for example by splaying the data symbols.
`
`In a combination of the TDMA/CDMA mobile radio system
`
`with the OFDMA multi-carrier procedure, optimal frequency
`
`resources for all communication links overseen by a base
`
`station can be allocated according to the invention with
`
`the help of a flexible referral of several sub—carriers or
`
`a segment of the frequency spectrum defined thereby. That
`
`is especially advantageous for applications with low power
`
`requirements — e.g., micro—cel1 systems — or for TDD
`
`I7
`
`18
`
`
`
`applications (Time Division Duplex) or for applications
`
`with higher data rates — e.g., for indoor systems, wireless
`
`systems or for applications with low movement speeds. By
`
`means of the improved frequency resource referral procedure
`
`(smart frequency hopping approach) according to the
`
`invention,
`
`interferences, especially the critical inter-
`
`cell interference and the inter—symbol interferences, are
`
`considered and at least reduced or compensated for. That is
`
`therefore of significance, since for almost all radio
`
`communication systems it is a typical characteristic,
`
`that
`
`they are limited in power downlink which is even reinforced
`
`by interference.
`
`Figure 3 shows the information flow across the radio
`
`interface for the allocation of the frequency resources to
`
`/7
`
`the mobile stations, MS, by the base station. Instead of /4
`
`a base station, BS, a base station control, BSC, can
`
`control the allocation but the base station, BS, always
`
`communicates through the air with the mobile stations, MS.
`
`ln an initial step (1)
`
`the mobile stations, MS, receive in
`
`a parallel manner all sub—carriers, oc,
`
`in the time slot,
`
`ts, assigned to them. For each sub~carrier, oc,
`
`the mobile
`
`station checks as a second step (2), whether an amplitude
`
`modulation is present in the data symbols transmitted in
`
`18
`
`19
`
`
`
`the time slot,
`
`ts, and thus has a measurement result about
`
`the quality of the respective sub—carrier, oc. It forms an
`
`average value from the results of the check for all sub-
`
`carriers belonging to a selected segment which results in a
`
`quality value for the entire segment. It can perform that
`
`for several segments — preferably in a parallel manner.
`
`Each mobile station, MS, determines in another step (3)
`
`according to_the knowledge of the quality of the various
`
`segments at least one suitable, preferred segment,
`
`for
`
`example segment Sx or Sa or Sm.
`
`t \
`
`In another step (4)
`
`the mobile station, MS, sends via
`
`the radio interface to the base station, BS, its priority
`
`
`lists, PL1 m PL3, with the information about several
`
` suitable segments,
`preferred,
`
` i.e.,
`
`about segments Sx, S3’,
`
`S2 or Sa, Sb,
`
`so or Sm, Sn, So for which a sequence of
`
`
`
`[Q5 suitability is determined by the mobile station, MS.
`I
`In the next step (5)
`the base station, BS, evaluates
`
`the incoming priority lists, PLl N PL3, with the
`
`information about the desired segments and decides — if
`
`necessary in a return conversation with the base station
`
`control, BSC - which segment was allocated to the
`
`respective mobile station, MS.
`
`In the example cited,
`
`the
`
`base station, BS, assigns the segments, Sx, Sa and Sm which
`
`were selected as the most suitable segments by the mobile
`
`19
`
`20
`
`
`
`station to the three mobile stations, MS. For the case
`
`. where the desired segment can not be allocated, one of the
`
`other segments is selected which were alternatively chosen
`
`by the mobile station, Ms.
`
`In a step (6)
`
`information about
`
`the allocated segments, Sx, Sa, and Sm is sent via the
`
`radio interface to the mobile stations, MS, which then use
`
`the received new frequency resources in the frequency
`
`spectrum for their individual communication links. To
`
`monitor as wide a frequency spectrum as possible the mobile
`
`stations, MS, each have a broadband receiver which is the
`
`case when using the OFDMA multiacarrier procedure. The
`
`point in time and thus the speed of the change of the
`
`allocation of radio resources and frequency resources can
`
`depend on the transmission conditions and/or the capacity
`
`utilization of a radio cell. It is basically possible per
`
`second in a relative frequency corresponding to the number
`
`of transmitted TDMA frames.
`
`In a mobile radio system based
`
`on a GSM standard, approximately 217 frames, for example,
`
`are transmitted per second.
`
`Figure 4 shows a schematic depiction of the amplitude
`
`modulation of the transmitted data symbols on a OFDMA sub-
`
`carrier to measure the quality of the segments through each
`
`mobile station.
`
`By converting possibly appearing
`
`interferences or noises into an amplitude modulation from
`
`20
`
`21
`
`
`
`data symbol to data symbol,
`
`the quality of the individual
`
`sub-carriers and thus the entire segment can be measured
`
`across all associated sub-carriers inya simple but
`
`effective manner. For every transmitted data symbol in a
`
`time slot an FFT signal processing is performed and the
`
`signal processing is continued in a carrier—selective
`
`8
`
`manner for the sub-carriers of the segment. There thus
`
`arises a resulting signal, rs, from a wanted signal, ss, by
`
`means of an interference signal or a noise signal,
`
`is, with
`
`a definite amplitude which lies between a maximum
`
`amplitude, Amax, and a minimum amplitude, Amin. If
`
`interference or noise is present,
`
`the amplitudes of the
`
`individual data symbols on a certain sub—carrier vary from
`
`data symbol to data symbol. If there is no interference or
`
`noise,
`
`the amplitudes of all data symbols manifest the same
`
`value. Relative deviations of the amplitudes of the data
`
`symbols can thereby be most easily determined, so that the
`
`absolute amplitude difference from data symbol to data
`
`symbol can be added up and the addition result can be
`
`normalized with the average amplitude of all data symbols
`
`transmitted to a predetermined sub—carrier.
`
`In this example
`
`the quality results of all 40 sub-carriers of the segment,
`
`Sx, are determined and an appropriate quality value is
`
`21
`
`22
`
`
`
`determined for the segment, Sx. This is also done for a
`
`variety of other segments and a number of segments of the
`
`best quality for a communication link is determined.
`
`A mobile station, MS,
`
`to support
`
`the procedure of the
`
`invention and the radio communication system is shown in
`
`Figure 5, while Figure 6 shows a corresponding base
`
`station, BS, or base station control, BSC. only depicted
`
`are the means and devices essential for the object of the
`
`invention.
`
`p The mobile station, MS, manifests a control means,
`MSE, with a storage device, MSP, and an FFT device, FFT, a
`
`means of modulation, MOD, or a means of demodulation, DEM,
`
`and a transmitter/receiver, MHF.
`
`Data symbols, d, of the participating signals are
`
`transmitted in both a down—link and up—1ink direction. For
`
`the transmission in an up—link direction they are processed
`
`by a control means, MSE, and are sent to the modulation
`
`means, MOD, for transmission. On the other hand,
`
`in the
`
`down-link direction data symbols, d, are received by the
`
`transmitter/receiver, MHF, are processed by the means of
`
`demodulation, DEM, and are sent on to the control means,
`
`DMSE. Data modulation, error protection, packaging, etc. are
`
`performed in a part of the means of modulation, MOD. In
`
`addition,
`
`the data symbols, d, of a radio block are splayed
`
`22
`
`23
`
`
`
`in a portion of the modulation means, MOD, corresponding to
`
`a combination of a TDMA and a CDMA procedure to achieve the
`
`fine structure specific to the individual link for the
`
`differentiation of the participating signals in a time
`
`slot. After an analog/digital conversion the radio blocks
`
`are amplified in the transmitter/receiver, MHF, and sent
`
`via the radio interface to the base station.
`
`In the down-link direction the transmitter/receiver
`
`means, MHF, receives all sub-carriers, oc,
`
`from the air in
`
`the time slot allocated to the mobile station, MS,
`
`-
`
`see
`
`step (1)
`
`in Figure 3. The control means, MSE,
`
`is informed
`
`by the sub-carriers, 0c, and conducts a measurement of the
`
`quality of various segments corresponding to the above
`
`variations. The control means, MSE, determines the suitable
`
`segments, S M, preferred for its own communication link,
`
`enters them in the priority list, and schedules the
`
`transmitter/receiver to transmit appropriate information
`
`through the air to the base station — see step (4)
`
`in
`
`Figure 3.
`
`The transmitter/receiver, MHF, also receives the
`
`/I
`information in the down—link direction Via the individual
`
`segment, S W, allocated by the base station — but at a
`
`later point in time after an evaluation of the transmitted
`
`23
`
`24
`
`
`
`segments of all mobile station by the base station a see
`
`step (6)
`
`in Figure 3. In keeping with the allocated
`
`frequency resources the control means, MSE, makes a
`
`/9
`
`/5
`
`change of the radio parameters in the radio cell for the
`
`mobile station, MS.
`
`At the same time because of the improved allocation
`
`procedure corresponding to the needs of the individual
`
`mobile stations, MS,
`
`the special transmission conditions
`
`(no CDMA or a multi-carrier procedure only within a certain
`
`bandwidth) and special data rates can be requested.
`
`The device according_to Figure 6 — designed as a base
`
`station, BS, or a base station control, BSC - manifests a
`
`-control means, BSE, with a memory means, BSP, and an FFT
`
`device, FFT, a modulation means, MOD, or a demodulation
`
`means, DEM, and a transmitter/receiver, BHF. The
`
`transmitter/receiver, BHF,
`
`is scheduled by the control
`
`means, BSE,
`
`to transmit through the air the sub—carriers,
`
`oc,
`
`in the down—link direction to the mobile stations.
`
`In
`
`the opposite direction the transmitter/receiver, BHF,
`
`receives information via the segments,
`
`S W, determined by’
`
`the mobile stations and sends it to the control means, BSE.
`
`Based on the evaluation of the totality of the incoming
`
`information,
`
`the control means, BSE, assigns a segment, S
`
`m,
`
`to each of its mobile stations and schedules the
`
`24
`
`25
`
`
`
`-
`
`transmitter/receiver, BHF,
`
`to transmit appropriate
`
`information through the air to the respective mobile
`
`station.
`
`The change of the segments of the frequency spectrum
`
`also considers the transmission conditions (strong
`
`impediments and interference) and the utilization capacity
`
`of the radio resources (time slots,
`
`frequencies, splay
`
`code)
`
`in the radio cell. These conditions are signaled to
`
`the control means, BSE, by the base station controller,
`
`BSC, or the Operation and Maintenance Center, OMC. Then the
`
`control means, BSE, selects the sub-carriers for the
`
`definition of the segment according to the quality
`
`characteristics for each communication link.
`
`The signal processing when using the OFDMA multi-
`
`carrier procedure by the FFT device as well as the
`
`modulation means, MOD, or the demodulation means, DEM,
`
`operates in the base station, BS,
`
`in the same manner as in
`
`the mobile station, MS, so that the above variants apply
`
`according to Figure 5. Stored in the memory device, BSP,
`
`are, among other things,
`
`the priority lists with the
`
`preferred suitable segments coming from the mobile
`
`stations.
`
`To achieve as simple as possible a synchronization in
`
`relation to time and frequency, an initial synchronization
`
`25
`
`26
`
`
`
`step is performed in which symbols with half transmission
`
`rates are sent, so that the transmitted symbols can be
`
`securely received in a time window, even with completely
`
`unsynchronized conditions. With the use of micro—cells
`
`only, a synchronization of the mobile stations to the base
`
`station is required.
`
`A base station code can be formed to identify the base
`
`station, whereby the phases of the data symbols transmitted
`
`between at least two adjacent sub—carriers at a first
`
`position in the radio block are used. Preferably these are
`
`two sub-carriers which lie in the center of a data stream
`
`with several sub-carriers. Thus the phase 0 degrees is
`
`assigned to the first data symbol on the sub—carrier with
`
`the lower frequency. The phase of the first data symbol of
`
`the a
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