CN1189946A - Multicarrier reverse link timing synchronization sytem, device and method - Google Patents
Multicarrier reverse link timing synchronization sytem, device and method Download PDFInfo
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- CN1189946A CN1189946A CN97190444A CN97190444A CN1189946A CN 1189946 A CN1189946 A CN 1189946A CN 97190444 A CN97190444 A CN 97190444A CN 97190444 A CN97190444 A CN 97190444A CN 1189946 A CN1189946 A CN 1189946A
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Abstract
The present invention provides a communication system, device and method of reverse link symbol timing synchronization of transmited signals to allow reverse link timing synchronization. A base unit transmits a forward link signal, receives a reverse link signal, and determines a timing offset for signals received on a reverse link timing synchronization channel, wherein the reverse link synchronization channel comprises a plurality of adjacent reverse link carrier frequencies that are utilized by a multicarrier subscriber unit to facilitate reverse link symbol timing synchronization. A plurality of multicarrier subscriber units receive a forward link signal and transmit a reverse link symbol timing synchronization burst on a reverse link timing synchronization channel wherein the reverse link timing synchronization channel comprises a plurality of adjacent reverse link carrier frequencies that are utilized by each subscriber unit, and adjusts a timing reference for transmitting signals to allow reverse link timing synchronization.
Description
The present invention relates to communication system, more particularly, relate to the multi-user's intercommunication system that effectively utilizes bandwidth.
As everyone knows, communication system comprises a plurality of subscriber units, and this subscriber unit communicates by the signal that transmits on wireless or cable network and one or more base or top end unit.Such communication system is a two-way radio communications system.In two-way radio communications system, Service Access Point comprises a transmitter and receiver usually by one, or the basic unit of transceiver provides.The base unit can be provided to another connection such as the network of public switched telephone network (PSTN), and wherein public switched telephone network (PSTN) is commonly referred to as PSTN.Because service inserts normally based on reservation (subscription-based) mode, so provide remote service to connect by an equipment that is called subscriber unit (Su).These subscriber units can generally include by RF spectrum and basic unit and communicate, the ambulatory transceiver device of " similar phone " handheld device.Each subscriber unit transmits information by sending a direction of signal base unit to basic unit.Subscriber unit can be known as reverse link signal or uplink signal to the signal that basic unit sends.The base unit transmits information by sending the signal that can be known as forward link signal or down link signal to subscriber unit.
Because the use to wireless communication system constantly is expanded, more available RF spectrum is just occupied.Thereby, wish that modern communication system can effectively utilize bandwidth.Orthodoxy Frequency Division Multiplex (OFDM) is a kind of multi-carrier modulation method well known in the prior art, this method allows a high-speed digital data stream is divided into one group of low-speed digital data flow, and all modulated independent data carrier signal of each low-speed digital data flow.As known in the prior art, the data carrier signal of modulation has different carrier frequencies, but carrier frequency is separated very closely, makes the frequency spectrum of adjacent modulating data carrier signal have the overlapping of demonstration.
Owing to have good bandwidth efficiency potentiality and, currently used OFDM in the broadcasting of digital audio broadcasting (DAB) and wire line MODEM and the wired application comprising but be not limited only to the resistivity of the channel impairments of some kind.And OFDM can be used to the forward link of multi-user's intercommunication system.In these are used, owing to multichannel modulating data carrier signal all produces in single transmitter unit, so (such as using discrete Fourier transform) controls the relation between them easily.Under the situation of DAB, in single transmission information source, produce simultaneously, add up and broadcast the modulating data carrier signal.Under the situation of communication system forward link, in single basic unit, produce simultaneously, add up and send the modulating data carrier signal.
Therefore, need a kind of reverse link time synchronization method, it should be highly suitable for having the system of the subscriber unit of transmission (Tx) multicarrier reverse link signal.
Fig. 1 is to use the sketch based on the intercommunication system of reverse link timing synchronization scheme of the present invention.
Fig. 2 is the module map that is used for the DSP/ASIC/ microprocessor of the basic unit of intercommunication system and subscriber unit, and this system uses based on reverse link timing synchronization scheme of the present invention.
Fig. 3 sends and receives the sequential sketch at the signal that does not have intercommunication system under the situation of propagation delay.
Fig. 4 sends and receives the sequential sketch at the signal that intercommunication system under the situation of propagation delay occurs.
Fig. 5 sends the signal of Fig. 3 and receive sequential chart to send and receive the sketch that sequential chart compares mutually with the communication system of using the reverse link timing synchronization at the signal that occurs under the situation of propagation delay.
Fig. 6 is the module map of a basic unit of diagram, and this base unit comprises one based on reverse link timing synchronization single carrier demodulation device of the present invention.
Fig. 7 is the module map of a basic unit of diagram, and this base unit comprises one based on tracing mode single carrier demodulation device of the present invention.
Fig. 8 is a diagram based on the legend of an embodiment of embodiment of initial access reverse link timing synchronization channel format of the present invention and tracing mode reverse link timing synchronization channel format.
Fig. 9 is the legend of diagram based on another embodiment of initial access reverse link timing synchronization channel format of the present invention.
The invention provides the reverse link symbol timing synchronization method of the communication system that a spectrum overlapping that is very suitable for effectively utilizing bandwidth on reverse link sends, wherein from a plurality of subscriber units, carry out the transmission of multichannel reverse link simultaneously, because the reverse link signal frequency spectrum of above-mentioned subscriber unit can be overlapping, so be referred to as overlapping bandwidth subscriber unit later on.
By control and coordinate parameter, can avoid the phase mutual interference between a plurality of overlapping bandwidth subscriber units that sending from the transmission signal of discrete overlapping bandwidth subscriber unit.By allowing at Fig. 1, the spectrum overlapping that carries out similar OFDM on the reverse link of the intercommunication system shown in the numbering 100 sends, the present invention allows the reverse link (150) of intercommunication system to obtain and the similar bandwidth efficiency of the forward link (160) of intercommunication system, supposes on the forward link of intercommunication system and uses OFDM.
In the present invention, provide a kind of reverse link symbol timing synchronization method that can use in system, this system has a plurality of overlapping bandwidth subscriber units that send on the spectrum overlapping reverse link of a similar OFDM.At first from a general case that is sending the overlapping bandwidth subscriber unit of reverse link signal.Reverse link signal is the digital modulation signals that comprises one or more modulating data carrier signal.The modulating data carrier signal is the carrier wave through the modulation of the digitized source in the transmitting element, wherein modulator approach can comprise M unit Quadrature Phase Shift Keying (M-PSK), M unit's quadrature amplitude modulation (qam) or any other Ditital modulation method known in the prior art.In OFDM, each carrier wave is commonly referred to as subcarrier or single-tone (tone).A modulating data carrier signal has its carrier frequency corresponding, symbol time benchmark and sign pulse shaping function.The symbol time benchmark is determined symbol regularly when the reverse link transmission takes place.From all known and the shaping pulse functions OFDM compatibility, select one and be used for shaping pulse function that the symbol in the modulation data carrier signal is modulated.The most general shaping pulse function is got a fixed value in shaping pulse function time delay.If the shaping pulse function keeps a fixed value in whole shaping pulse process, then this function is commonly referred to as rectangular pulse shaping function.Be defined in the optimum embodiment equation below of an impulse function gv (t).
In this shaping pulse definition, from 0 to t
sShaping pulse part after this be known as useful symbolic component, and t
sBe known as useful symbol time delay.From t
sTo T
sShaping pulse partly be to be commonly referred to as cyclic extensions, cycle expansion or protection sign extension at interval.The cyclic extensions part can be placed in before the useful symbolic component rather than afterwards, also can be known as a Cyclic Prefix in this case.Occurring in OFDM, using cyclic extensions can improve performance under the situation of multi-path channel sometimes.
Consider a ofdm signal based on defined shaping pulse.In an optimum embodiment, can on a forward link, send this signal by single basic unit to a plurality of overlapping bandwidth subscriber units.Following equation has illustrated an ofdm signal based on defined shaping pulse function gv (t), x (t).N provides the quantity of the subcarrier that is used to send.X
K, mProvide the symbol that is sent, and A (t) e
jΦ
(t)Provide the rotation of fading channel and phase place.
Because the modulating data carrier signal of all bag ofdm signal has identical symbol time benchmark and with 1/t
sThe interval be carried out frequency separation, so any overlapping bandwidth subscriber unit all can be in the data that detect under the situation of the modulating data carrier-in-interference that is not subjected to other on any modulating data carrier wave.By being t a length
sThe set time window on the ofdm signal that receives carried out integration carry out this detection.Following equation has illustrated under the situation of given reception ofdm signal x (t) by p
ThThe detection that individual overlapping bandwidth subscriber unit carries out n symbol.
Consider the situation of modulating data carrier signal now from two independent overlapping bandwidth subscriber units, wherein each overlapping bandwidth subscriber unit all sends a reverse link signal with a modulating data carrier signal, and each modulating data carrier signal all has different carrier frequencies, but has the overlapped signal frequency spectrum.In this case, owing to overlapping bandwidth subscriber unit separates physically, so they comprise independent local frequency, time reference and phase reference.These local benchmark all are to be based upon on the basis of local oscillator contained in each overlapping bandwidth subscriber unit.Also be noted that the difference owing to propagation path, the decay of second overlapping bandwidth subscriber unit reverse link signal and phase place rotation are different from first unit.Can express the composite signal of comprising that receives in basic unit by following equation from the summation of two overlapping bandwidth subscriber unit reverse link signal.By the equation part of k=0 sign corresponding to the signal that on first reverse link, sends, and by the equation part of k=1 sign corresponding to the signal that on second reverse link, sends.Time reference and local frequency benchmark are represented by δ k and ν k respectively.Note, because equation has been represented the signal that receives in basic unit, so any propagation delay differences between basic unit and two subscriber units all is the parts in the variable of express time benchmark.A
k(t) represent the decay that channel causes, e
J Ф k (t)The phase place rotation that expression channel or local phase datum offset cause.
When modulating data carrier wave from first reverse link is attempted to detect in basic unit, there is interference usually from second reverse link.This interference is that the mismatch by the time reference of two overlapping bandwidth subscriber units or local frequency benchmark causes.Following equation has illustrated n the detection that signal carries out to sending on first reverse link, supposes that wherein the time reference synchronous situation is good and have mismatch between the local frequency benchmark.Particularly, two reverse link signal regularly arrive basic unit with identical symbol, but no longer with 1/t
sInteger multiple as the interval of frequency separation.Represent δ 0=0, δ 1=0, ν 0=0 and ν 1 ≠ 0 with mathematical way.
Suppose the symbol of the signal that receives from basic unit have between regularly good synchronously, if the mismatch between the local frequency benchmark becomes 0 shown in following equation, the distracter that then provides previously can disappear:
For the present invention, following equation illustrated at n the detection that symbol carried out that sends on first reverse link, suppose have between two local frequency benchmark good synchronously and between time reference, have a mismatch.Two reverse link signal are with 1/t
sInteger multiple arrive basic unit as frequency interval, but no longer have identical symbol regularly.Represent with mathematical way, ν 0=0, ν 1=0, δ 0=0, δ 1 ≠ 0.
According to the value of δ 1, the equation that detects n symbol has a kind of form in three kinds of forms.CASE?1：-T
s＜δ
1＜-T
s+t
s 
CASE?2：-T
s+t
s＜δ
1＜0
CASE?3：0＜δ
1＜+t
s 
These three kinds of detections can be summarized as following equation from the situation of n symbol of the first overlapping bandwidth subscriber unit.
Note when regularly mismatch distracter disappearance in the above-mentioned equation near zero time of symbol.And note the use of cyclic extensions has been alleviated the regularly equal requirement of symbol that two reverse links are sent.Timing base can differ the quantity that can reach the cyclic extensions time delay at most.Promptly in order to make second reverse link signal not disturb first reverse link signal, be-Δ t to the requirement of second reverse link signal
s＜δ 1＜0.
Although above-mentioned analysis is at single, from two overlapping bandwidth subscriber units and have near t
sThe modulating data carrier wave in carrier spacing provide, but this analysis also is applicable to have more than two overlapping bandwidth subscriber unit with near 1/t
sThe situation in carrier spacing of arbitrary integer multiple.
For fear of the phase mutual interference, communication system must be controlled the local frequency benchmark and the symbol time benchmark of each overlapping bandwidth subscriber unit in a kind of predetermined mode.The requirement of frequency reference is with 1/t
sThe frequency interval of integer multiple separate the modulating data carrier frequency.The requirement of time reference is that all reverse link signal regularly arrive basic unit with identical symbol, this means no matter that user has sent symbol, and be to begin receiving symbol on the identical timing section for the basic unit symbol clock with respect to all.Notice that shown in the equation of front, the amplitude and the phase difference that arrive the reverse link signal of basic unit under the situation of suitable control frequency and symbol timing parameters can not produce interference.Current the analysis showed that, by use a kind of 1/t that has between from the modulating data carrier wave of independent overlapping bandwidth subscriber unit reverse link signal
sSo few frequency interval can be realized a kind of multi-user's reverse link that effectively utilizes bandwidth, even and the frequency spectrum of reverse link signal overlap, also can avoid the phase mutual interference.
By a kind of reverse link timing synchronization (RLSTS) method is provided, the present invention proposes the timing synchronization characteristic.Although the equation set of front has been pointed out the importance of reverse link timing synchronization in the system with overlapping bandwidth subscriber unit, even but under the nonoverlapping situation of reverse link signal frequency spectrum of different subscriber units, the present invention also is very useful for the system with multicarrier reverse link signal.By all reverse link signal being provided regularly synchronously, the present invention allows basic unit to use the symbol sampler section of identical detection from the reverse link signal of all subscriber units, thereby has simplified basic unit greatly.In the system that combines such as the multi-carrier modulation of OFDM and time division multiple access (TDMA), the symbol sampler section that the present invention allows to detect reverse link signal remains unchanged on all reception tdma slots.
Notice that in a system based on TDMA, by monitoring that the reception forward link signal that basic unit sends obtains the received signal symbol, time slot and frame are regularly usually for subscriber unit.Referring to Fig. 3, numbering 300.Can determine like this that reverse link time slot and frame are regularly, make reverse link frame be offset in the set time, α and numbering 310 places begin, this skew is for the section start of a forward link frame, wherein section start time of forward link frame by fixed during to basic unit on base or the timing base 320.As Fig. 4, the numbering 400 shown in, subscriber unit apart from basic unit situation far away under, can produce bigger propagation delay.If subscriber unit uses the timing that receives forward link signal to determine the timing that its reverse link signal sends, to compare with basic unit timing base, propagation delay can send at the reverse link of subscriber unit and produce a delay in the timing base.Correspondingly, the transmit path from subscriber unit to basic unit can experience identical propagation delay.This propagation delay and numbering 410 are expressed as
Δ=d/c wherein d is a distance from basic unit to subscriber unit, and c is the propagation velocity (3 * 10 of light free space
6And Δ is to be the propagation delay of unit with the second m/s).Thereby, if subscriber unit only is to send reverse link signal with respect to the benchmark that obtains according to a forward link signal constant offset regularly, then compare with the time α (320) that reaches near the subscriber unit basic unit, the time that reverse link signal arrives basic unit is α+2 Δs (420).Quantity 2 Δs are commonly referred to as round-trip propagation delay or round-trip delay done in abbreviation.For example, consider the subscriber unit of a basic unit 3km of distance.The round-trip propagation delay of such system is 20 μ Sec.For a subscriber unit 0FDM communication system can be from basic unit far away, any significant delay all can receive from basic unit from remote and near the symbol of signal of subscriber unit produce difference between regularly.Shown in the equation of front, the situation that this symbol regularly can not align can produce the phase mutual interference.Though,, use long cyclic extensions not expect in many cases owing to use long cyclic extensions can lower the bandwidth efficiency of system by using long cyclic extensions can alleviate the influence of this delay.The present invention uses this method can adjust the symbol timing base of each subscriber unit for multi-carrier communications systems provides a kind of method, thereby makes the reverse link signal from different subscriber units regularly arrive basic unit with identical symbol.Regularly mean it is the symbol that unit in a plurality of subscriber units sends no matter have identical symbol, the symbol that is received all is to begin on identical time period for base/timing base with respect to basic unit the time.
More specifically, the invention provides a kind of multicarrier reverse link timing synchronization (RLSTS) method.In an optimum embodiment of the system that uses the RLSTS method, subscriber unit shifts to an earlier date 2 Δs to the transmitting time of its reverse link signal, thereby has eliminated the influence of propagation delay to the signal of basic unit reception.As Fig. 5, shown in the numbering 500, the feasible reverse link signal that sends from a remote subscriber unit of this transmission timing advance has the regularly identical symbol timing of symbol of the signal that sends with the proximal subscribers unit when arriving basic unit.Attention RLSTS method must be estimated round-trip propagation delay.And, in case known this delay, preferably periodically follow the tracks of with respect to the position change of basic unit or upgrade round-trip propagation delay, thereby keep accurate round-trip delay estimation along with subscriber unit.Because the present invention can find the also deviation of correcting user unit timing base when propagation delay changes, thus location of subscriber unit not fixedly the time periodically updating of RLSTS also be useful.
In optimum embodiment of the present invention, can treat initial acquisition respectively and then follow the tracks of the problem of round-trip propagation delay.As known in the prior art, the forward link signal that the first meeting of subscriber unit sends according to the base station obtain symbol and frame level other regularly.After obtaining this timing, subscriber unit can carry out once initial RLSTS channel access, comprising RLSTS message at the RLSTS channel of format, and transmission sends the RLSTS pulse train that comprises RLSTS message by reverse link on preset time.The scheduled time preferably is on the scheduled time offset alpha with respect to the timing base point the signal that receives from basic unit.The digital coding that RLSTS message is preferably at random a kind of or unique, so that given user and other, the subscriber unit that can attempt initial access in the identical time distinguishes.Owing to there is a round-trip propagation delay, can be than near the pulse train of the subscriber unit basic unit late 2 Δs of Initial R LSTS channel access pulse train arrive basic unit second.Base unit measure R LSTS pulse train can be from known moment that a near subscriber unit arrives and the time migration between the actual time of arrival, thereby determines round-trip propagation delay.After determining round-trip delay, basic unit carries out RLSTS and confirms.RLSTS affirmation process comprises that sending the RLSTS that comprises a RLSTS acknowledge message on the forward link confirms pulse train.RLSTS message preferably comprises unique coding of measuring timing slip and receiving in reverse link RLSTS pulse train.Unique coding preferably is used to confirm send the identity of the subscriber unit of RLSTS pulse train.Then receive the subscriber unit that RLSTS confirms pulse train and shift to an earlier date follow-up transmitting time by time delay α being shortened into α-2 Δ (510), make when follow-up being sent in arrives basic unit symbol regularly with subscriber unit near basic unit the time observed symbol timing identical.
The first step in the initial acquisition process is that subscriber unit uses a kind of method known in the prior art to determine from the symbol timing of the signal of basic unit reception.For the time that sends signal from basic unit, this regularly has been delayed Δ.Then subscriber unit must be derived other timing of frame level of forward link signal.Can accomplish this point by a kind of in the several method of the prior art, the preassigned pattern that sends on such method and the predetermined point of basic unit in each frame is relevant.
As previously mentioned, subscriber unit determine the symbol of the signal that basic unit sends and frame regularly after, subscriber unit carries out initial RLSTS channel access.Preferably sending the RLSTS pulse train on the scheduled time regularly with respect to forward link frame.
Note, the RLSTS pulse train when arriving basic unit because of existing round-trip delay may not have suitable symbol regularly.For fear of the modulating data carrier wave that disturbs on the adjacent carriers frequency, several carrier waves on RLSTS pulse train both sides have constituted the part of TLSTS channel in the system.The concrete quantity of this carrier wave depends on such as the modulating pulse shaping, and in the carrier spacing, selected modulation system is to the sensitivity of interference and the system parameters of the maximum serious forgiveness of channel.
In an optimum embodiment, before carrying out Initial R LSTS channel access subscriber unit not with basic unit communication.Thereby the trial of Initial R LSTS channel access is not coordinated between a plurality of subscriber units.Owing to do not coordinate, so two or more subscriber unit may attempt to carry out the RLSTS channel access simultaneously.This not coordinated visit is known as based on contention.In visit based on contention, if a subscriber unit is than the more approaching basic unit of another subscriber unit, then the signal from nearer subscriber unit has enough intensity so that received by basic unit, even also be like this under the situation of appearance from the interference of farther unit.Notice that subscriber unit nearer or far away does not know that all other subscriber unit has carried out the RLSTS channel access.Thereby, do not comprise during if basic unit R LSTS confirms identity validation at the information of subscriber unit, then two subscriber units can suppose that all this message is to send at its RLSTS channel access, thereby cause unit far away to use wrong round-trip delay.As previously mentioned, for fear of this problem, subscriber unit is preferably in and comprises a code word unique or that produce at random in the RLSTS message that sends by the RLSTS pulse train.When basic unit carries out a RLSTS affirmation, unique coding and round-trip delay estimation in confirm the RLSTS acknowledge message that pulse train sends by RLSTS, have been comprised.Under the above-mentioned situation that captures proximal subscribers unit reverse link signal, can comprise unique coding in the RLSTS acknowledge message from the proximal subscribers unit.Because the coding that comprises in the RLSTS message of this coding and subscriber unit far away does not match, so this subscriber unit is ignored this data.Subscriber unit far away in this case preferably carries out an extra RLSTS channel access so that enable RLSTS.Because of second problem lack coordinating between subscriber unit to produce carries out occurring when RLSTS channel access and its signal arrive basic unit with almost equal power level at two or more subscriber units simultaneously.In this case, the mutual serious interference of signal, feasible correctly received signal.This situation is known as conflict.In this case, basic unit does not preferably carry out any affirmation, perhaps can be by detecting the appearance that high level received signal intensity detected and reported conflict.If just noticing, two subscriber units lack that RLSTS confirms or about the report of conflict and repeat the RLSTS channel access one time, then two unit can be attempted visit simultaneously once more, thereby cause another time conflict.For fear of this situation, subscriber unit is waited for a time period of determining at random before being preferably in repetition RLSTS channel access.If window is sufficiently long at random, the probability that multiple conflict then takes place becomes very little, even and to finish the required time of Initial R LSTS process when an Initial R LSTS channel access conflict takes place also be quite short.This scheme of avoiding multiple conflict is similar to a kind of known, general ALOHA method in block data system.
When basic unit receives a RLSTS pulse train, determine that the symbol of received signal regularly and this symbol is regularly regularly compared with the symbol of expectation.In the present invention, except the RLSTS channel, receive in the ofdm system all other reverse link signal by known symbol and slot timing.By in demodulating process each symbol on these carrier waves only being used a sample, ofdm demodulator can utilize these characteristics, thereby has simplified the hsrdware requirements of demodulation greatly.But this priori about the timing of reverse link symbol can not show on the RLSTS channel.
As Fig. 6, shown in the numbering 600, in another optimum embodiment, basic unit demodulator comprises the demodulator (620) of the reverse link signal on an ofdm demodulator based on FFT (610) and the independent demodulation RLSTS channel.This demodulator is preferably with the high sampling rate work such as 128 sample per seconds.Note, for Fig. 8, the RLSTS channel format of numbering 800, this receiver can be used to an initial access of demodulation (IA) RLSTS pulse train or tracking (Tr) RLSTS pulse train.Notice that active transmission (Trf) channel also can take a part and follow the tracks of channel.This demodulator preferably comprise one be tuned to become transducer under the numeral of carrier frequency of RLSTS pulse train, a digital matched filter and a symbol timing estimator, wherein digital matched filter is a running integral device under the situation of carrying out rectangle sign pulse shaping transmission.A kind of symbol timing recovery method known in the prior art can be used to determine the symbol timing of the reverse link RLSTS signal that receives by the RLSTS channel.After definite symbol timing, calculate the difference between actual time of arrival and the expected approach time.And the content that detects the RLSTS pulse train is so that the code word in the taking-up RLSTS message.This information is then linked and is sent back to subscriber unit by previously described RLSTS affirmation process.
Subscriber unit receive confirm from the RLSTS of basic unit and confirm that code word that code word in the RLSTS acknowledge message and subscriber unit are sent is complementary after, subscriber unit is adjusted it and is sent regularly with the compensation round-trip delay.Each overcome the transmission of messages mistake that low quality RF channel may be introduced, subscriber unit preferably can carry out another time RLSTS channel access and produce correct result so that confirm first RLSTS process.Preferably send regularly and confirm that follow-up RLSTS channel access has produced and has the RLSTS acknowledge message that approaches 0 timing adjusted value substantially and realize this point by upgrading subscriber unit in the above described manner.
Tracking modes of operation has significant difference with the initial access pattern aspect five.First aspect, the symbol of a signal regularly can be fully near ideal value to prevent to disturb contiguous carrier wave.This has eliminated the demand to multicarrier in the RLSTS channel, then needs this multicarrier in the initial access section.Second aspect for the change of moving the round-trip delay that is caused of Continuous Tracking subscriber unit, is preferably carried out RLSTS with recursive fashion.The third aspect, owing to set up before carrying out tracing mode RLSTS channel access and the communicating by letter of basic unit, these tracing modes visits are preferably dispatched in the priori mode in basic unit.Preferably the dispatch notification of tracing mode RLSTS channel access is arrived subscriber unit by forward link.The example embodiment that tracing mode is upgraded scheduling is that the timeslot number one in the each ten tdma frame is assigned to first subscriber unit, and the timeslot number two in the each ten tdma frame is assigned to second subscriber unit.Owing to do not have two subscriber units to visit the RLSTS channel with tracing mode simultaneously, so there is no need to handle the contention in the optimal tracking pattern.Fourth aspect, owing to often use the quantity of the subscriber unit of communication channel to be far longer than the quantity of most time at the subscriber unit that carries out initial access, and because tracing mode visit needs periodic visit, so the occurrence frequency that RLSTS is carried out the tracing mode visit is far longer than the access frequency of initial access pattern.The 5th aspect, because subscriber unit has carried out once initial regularly adjustment according to initial access RLSTS process, so the timing slip that basic unit is measured in tracing mode RLSTS channel access is not a round-trip propagation delay, but still equal required in the subscriber unit timing base, on basic unit, make round-trip propagation delay become 0 adjustment amount.The timing slip of measuring with tracing mode can be known as the apparent round-trip delay.Though these difference are that significantly the basic structure of the RLSTS process of two kinds of different modes is very similar.
When being in the initial access pattern, subscriber unit is preferably derived forward link symbol according to the forward link signal that receives from basic unit, and time slot and frame are regularly.Reverse link timing base value can be based on the deviant of the determined value of initial access RLSTS process.Subscriber unit can be with predetermined, and preferably periodic interval is visited the RLSTS channel and sent the RLSTS pulse train.But, different with initial access RLSTS channel, because known pulse train can arrive basic unit in the little deviation range of expected approach time, the carrier wave so tracking RLSTS channel does not need protection.Thereby, follow the tracks of the RLSTS pulse train and can not disturb contiguous data-modulated carrier wave.The base unit must determine once more that the RLSTS pulse train switches to the time of reaching really with respect to expected approach time, and confirms this information is sent to subscriber unit by a RLSTS.If the RLSTS pulse train arrived before the timing of basic unit wishes, then basic unit R LSTS affirmation can comprise a negative apparent round-trip delay, thereby subscriber unit can postpone its timing base.If the RLSTS pulse train arrives after the timing of basic unit wishes, then basic unit R LSTS affirmation can comprise a positive apparent round-trip delay, thereby subscriber unit can shift to an earlier date its timing base.Because the required timing of tracing mode changes very little, so apparent round-trip delay information can be quantized into an independent position, wherein this information bit is set as positive apparent round-trip delay of indication, make subscriber unit shift to an earlier date a bit of symbol time delay Δ t to transmitting time, perhaps remove this information bit to indicate a negative apparent round-trip delay, make subscriber unit postpone a bit of symbol time delay Δ t to its transmitting time.
Because a faults can cause the subscriber unit transmitting time of 2 Δ t to be in error state at most, rather than cause the gamut time value of transmitting time window all to be in error state, so when faults occurring this process than transmission stalwartness with actual apparent round-trip delay.But,, need more frequent RLSTS channel access owing to can not change transmitting time in a large number by an independent RLSTS channel access usually.Notice that several mutation of unit process are within the scope of the present invention, allow to carry out 4 kinds of different transmitting time adjustment thereby for example send 2 positions, thereby and comprise a coding permission sending instantaneous any change of not doing.
In another optimum embodiment, carry out more newly arriving under the tracing mode by the reverse link signal data-modulated carrier wave that only uses the information of carrying and improve the bandwidth efficiency of reverse link.State a kind of acquisition methods in the use and obtain after the initial timing synchronously, the user preferably uses OFDM transmission information on reverse link.Do not allow subscriber unit periodically send the RLSTS pulse train in embodiment in front, basic unit uses one or more reverse link signal data-modulated carrier wave that carries information to measure symbol timing deviation under tracing mode.By using an existing reverse link signal of carrying information to measure symbol timing deviation, tracing mode RLSTS channel can be cancelled, thereby has improved the bandwidth efficiency of system.Be that an optimum about this method is realized in the basic unit below.The base unit comprises one or more single carrier demodulation device (710), each demodulator is preferably realized with change transducer and digital matched filter under the numeral, wherein shown in Fig. 7 (700), matched filter is a slip rectangular window integrator under the situation of using OFDM.By using a kind of symbol timing recovery method well known in the prior art, the output of single carrier demodulation device is used to the symbol timing deviation of measuring reverse link signal.Under the situation of a plurality of subscriber units and basic unit communication, basic unit periodically become under the numeral transducer be tuned on one or more carrier frequency of using in a sequential manner by subscriber unit.In an embodiment with a plurality of single channel demodulators, a plurality of demodulators are used to obtain simultaneously the symbol timing deviation on a plurality of carrier frequencies.If a plurality of carrier frequencies are used simultaneously by a plurality of subscriber units, basic unit can be simultaneously, rather than obtain the symbol timing deviation of a plurality of subscriber units in order.If a plurality of carrier frequencies are used by an independent subscriber unit, basic unit can be by comprehensively obtaining having the symbol timing deviation estimation of improved accuracy from the timing slip information of a plurality of demodulators.
For the RLSTS channel that must visit several constraints are arranged.As previously mentioned, the quantity of tracing mode RLSTS channel access can be considerably beyond the quantity of the RLSTS visit that is used for initial access.And before initial access, subscriber unit must be known the position of a RLSTS channel.By such channel is placed on the predetermined carrier wave, perhaps require periodic broadcasting its position in basic unit to address this problem.As previously mentioned, the RLSTS channel that is used for initial access must comprise several carrier waves to prevent to disturb the transmission of other subscriber unit on the adjacent carriers.In order to describe, suppose that reverse link is a tdma system.And 2 carrier waves on supposition initial access RLSTS pulse train both sides are enough to prevent any remarkable interference at the modulating data carrier wave on the adjacent carrier frequencies.Fig. 8 has illustrated such channel that satisfies these requirements in the numbering 800, carries out initial access RLSTS on the carrier wave N in time slot 0 (810).Carrier wave N-2, N-1, N+1 and N+2 (820) are as the protection frequency band in the RLSTS channel in the time slot 0.Can be at the enterprising line trace pattern of any carrier wave RLSTS channel access among the carrier wave N-2 to N+2 in the time slot 1 to 7 (830).Notice that these carrier waves and time slot combination also can be used to received pronunciation or transfer of data, and are distributed by basic unit.So just allow to carry out resource allocation very flexibly.For example, if system supports that at present a large amount of low speed voice transfer and many calcellations unit is in active state simultaneously, then needs many tracing mode RLSTS channel access, and can specify the most of time slots in these time slots to be used for tracing mode RLSTS.If system only supports some high-speed data users at present, then the great majority in these the time slot-carrier combination in the RLSTS channel can be assigned to user's use to support its transfer of data.In a wideband OFDM system, on whole reverse link frequency band, insert several such RLSTS channels at interval.The inventor recognizes that there are several different expansions in this basic conception, and these expansions have different basic functions and divide on frequency and time, and wherein these expansions are similar substantially with above-mentioned notion, and are considered to fall within the scope of the present invention.
As Fig. 9, shown in the numbering 900, in another optimum embodiment, the RLSTS pulse train that the RLSTS channel supports subscriber unit to carry out on multicarrier on frequency and single symbol time delay sends.In this embodiment, each symbol of RLSTS message is assigned on the different carrier frequencies, and uses OFDM to send the RLSTS pulse train on a symbol time delay.In this embodiment RLSTS channel (910) can comprise more than or equal some carrier waves of the symbol quantity in the RLSTS message and have time interval greater than the time delay of a symbol time delay, wherein distribute the time interval in the mode in every time interval of frame.
In order to prevent to disturb the transmission of other subscriber unit, the time interval must have the time delay greater than a symbol time delay.If round-trip propagation delay is less than a symbol time delay, then optimum time delay is two symbol time delays.If round-trip propagation delay greater than a symbol time delay, then must increase time interval time delay.Fig. 9 shows a RLSTS channel (910) based on this embodiment.Can realize the function described in the RLSTS method easily by some current techiques, these technology comprise Fig. 2, the DSP shown in the numbering 200, ASIC, microprocessor (202,204) and similarly installing.
Claims (10)
1. communication system wherein comprises:
1A) basic unit, this unit sends forward link signal, the timing slip of the signal that receives reverse link signal and determine to receive by reverse link timing synchronizing channel, wherein the reverse link synchronizing channel comprises a plurality of adjacent reverse link carriers frequency of being used by a multicarrier subscriber unit, so that can carry out the reverse link timing synchronization;
1B) a plurality of multicarrier subscriber units, wherein each subscriber unit receives forward link signal, send regularly synchronization burst of reverse link by reverse link timing synchronizing channel, and adjustment is used to send the timing base of signal so that can carry out reverse link regularly synchronously, and wherein reverse link timing synchronizing channel comprises a plurality of adjacent reverse link carriers frequency of being used by each subscriber unit.
2. communication system as claimed in claim 1 wherein comprises a bit among the 2A-2C at least:
2A) reverse link timing synchronizing channel also comprises predetermined time interval;
2B) each subscriber unit to reverse link regularly the visit of synchronizing channel be based on contention; And
2C) each subscriber unit is with recurrence scheduling mode visit reverse link timing synchronizing channel.
3. communication system wherein comprises:
3A) basic unit, this unit sends forward link signal, the timing slip of the signal that receives reverse link signal and determine to receive by reverse link timing synchronizing channel, wherein synchronizing channel comprises a plurality of adjacent reverse link carriers frequency of being used by a subscriber unit, so that can carry out the reverse link timing synchronization;
3B) a plurality of multicarrier subscriber units, wherein each subscriber unit receives forward link signal, send reverse link timing synchronization pulse train by one first reverse link timing synchronizing channel, and adjust and be used to send the timing base of signal so that can follow the tracks of the regularly synchronous renewal of reverse link, wherein first reverse link regularly synchronizing channel comprise predetermined time interval and a plurality of adjacent reverse link carriers frequency so that can carry out initial reverse link regularly synchronously, and use regularly synchronizing channel of second reverse link that comprises predetermined time interval and at least one reverse link carriers frequency.
4. communication system as claimed in claim 3 wherein comprises a bit among the 4A-4C at least:
4A) reverse link timing synchronizing channel also comprises predetermined time interval;
4B) each subscriber unit to reverse link regularly the visit of synchronizing channel be based on contention; And
4C) each subscriber unit is with recurrence scheduling mode visit reverse link timing synchronizing channel.
5. multicarrier subscriber unit wherein comprises:
5A) reverse link timing synchronous generator, this generator links to each other with a transmitter, for reverse link timing synchronizing channel produces a format reverse link timing synchronization message, and produce one and comprise the regularly reverse link timing synchronization pulse train of synchronization message of format, wherein reverse link timing synchronizing channel has a plurality of adjacent reverse link carriers frequencies at least;
5B) timing base adjustment unit, this unit and a transmitter, a receiver links to each other with reverse link timing synchronous generator, and adjusts the transmission timing of reverse link signal according to the timing slip message that obtains from forward direction link received signal;
5C) with the reverse link transmitter that links to each other with the timing base adjustment unit of synchronous generator regularly, this transmitter sends the reverse link signal that comprises reverse link timing synchronizing signal;
5D) the receiver that links to each other with the timing base adjustment unit, this receiver receives the forward link signal that comprises timing slip message;
6. multicarrier subscriber unit as claimed in claim 5 wherein comprises a bit among the 6A-6F at least:
6A) reverse link timing synchronizing channel also comprises predetermined time interval;
6B) wherein each multicarrier subscriber unit to reverse link regularly the visit of synchronizing channel be based on contention;
6C) each multicarrier subscriber unit is with recurrence scheduling mode visit reverse link timing synchronizing channel;
6D) reverse link timing synchronization message comprises the coding of a sign multicarrier subscriber unit;
6E) the multicarrier subscriber unit sends reverse link timing synchronization pulse train by a single carrier of reverse link timing synchronizing channel;
6F) the multicarrier subscriber unit sends reverse link timing synchronization pulse train in single symbol time interval of reverse link timing synchronizing channel.
7. basic unit wherein comprises:
7A) receiver, this receiver receives reverse link timing synchronization pulse train, this pulse train comprises a reverse link timing synchronization message that receives by reverse link timing synchronizing channel, and reverse link timing synchronizing channel has a plurality of adjacent reverse link carriers frequencies;
7B) reverse link timing synchronizing signal analyzer that links to each other with receiver, this analyzer is measured regularly timing of synchronization message of reverse link, and a timing of measuring and a predetermined benchmark are regularly compared to determine a timing slip value;
7C) timing slip message generator that links to each other with reverse link timing synchronizing signal analyzer, this generator produces a timing slip message according to the timing slip value;
7D) transmitter that links to each other with the timing slip message generator, this transmitter sends a forward link signal that comprises timing slip message.
8. basic unit as claimed in claim 7 wherein comprises a bit among the 8A-8E at least:
8A) reverse link timing synchronizing channel also comprises predetermined time interval;
8B) subscriber unit to reverse link regularly the visit of synchronizing channel be based on contention;
8C) subscriber unit is visited regularly synchronizing channel of reverse link with the recurrence scheduling mode:
8D) also comprise a tracing mode single carrier demodulation device that links to each other with receiver, a dull system data carrier of this demodulator multicarrier reverse link signal that demodulation is received according to modulating data carrier frequency sequential scheduling, and the symbol timing deviation of estimation modulating data carrier wave, wherein according to modulating data carrier frequency sequential scheduling with the different dullness system data carrier of different time interval demodulation; And
8E) also comprise a reverse link timing synchronization single carrier demodulation device that links to each other with receiver, this demodulator demodulation is by a single carrier of the reverse link timing synchronization pulse train of reverse link timing synchronizing channel reception, and the symbol timing deviation of estimation reverse link timing synchronization pulse train.
9. method that is used for the reverse link timing synchronization, comprising step have:
9A) be a regularly format of synchronizing channel generation reverse link timing synchronization message of reverse link, and produce one and comprise the regularly reverse link timing synchronization pulse train of synchronization message of format, wherein reverse link timing synchronizing channel has a plurality of adjacent reverse link carriers frequencies at least;
9B) transmission of adjusting reverse link signal according to the timing slip message that obtains from forward direction link received signal regularly;
9C) send the reverse link signal that comprises reverse link timing synchronizing signal;
9D) receive the forward link signal that comprises timing slip message.
10. method as claimed in claim 9 wherein comprises a bit among the 10A-10C at least:
10A) reverse link timing synchronizing channel also comprises predetermined time interval;
10B) each multicarrier subscriber unit to reverse link regularly the visit of synchronizing channel be based on contention;
10C) each multicarrier subscriber unit is with recurrence scheduling mode visit reverse link timing synchronizing channel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN97190444A CN1189946A (en) | 1996-04-26 | 1997-04-11 | Multicarrier reverse link timing synchronization sytem, device and method |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/639,155 | 1996-04-26 | ||
| CN97190444A CN1189946A (en) | 1996-04-26 | 1997-04-11 | Multicarrier reverse link timing synchronization sytem, device and method |
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| CN1189946A true CN1189946A (en) | 1998-08-05 |
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| CN97190444A Pending CN1189946A (en) | 1996-04-26 | 1997-04-11 | Multicarrier reverse link timing synchronization sytem, device and method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1328869C (en) * | 1999-04-23 | 2007-07-25 | 高通股份有限公司 | Method and device for transmitting synchronous channel message in multicarrier communication system |
| US8724617B2 (en) | 2009-09-15 | 2014-05-13 | Huawei Technologies Co., Ltd. | Uplink synchronization processing method, user equipment, and base station |
-
1997
- 1997-04-11 CN CN97190444A patent/CN1189946A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1328869C (en) * | 1999-04-23 | 2007-07-25 | 高通股份有限公司 | Method and device for transmitting synchronous channel message in multicarrier communication system |
| US8724617B2 (en) | 2009-09-15 | 2014-05-13 | Huawei Technologies Co., Ltd. | Uplink synchronization processing method, user equipment, and base station |
| US9131435B2 (en) | 2009-09-15 | 2015-09-08 | Huawei Technologies Co., Ltd. | Uplink synchronization processing method, user equipment, and base station |
| US9220077B2 (en) | 2009-09-15 | 2015-12-22 | Huawei Technologies Co., Ltd. | Uplink synchronization processing method, user equipment, and base station |
| US9743366B2 (en) | 2009-09-15 | 2017-08-22 | Huawei Technologies Co., Ltd. | Uplink synchronization processing method, user equipment, and base station |
| US10536912B2 (en) | 2009-09-15 | 2020-01-14 | Huawei Technologies Co., Ltd. | Uplink synchronization processing method, user equipment, and base station |
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