MXPA00004691A - Broadcast network selection techniques for hybrid radiocommunication systems comprising both a cellular communication system and a radio broadcast system - Google Patents

Abstract

Hybrid cellular/broadcast systems are described wherein broadcast (simulcast) techniques are used to provide high data rate, downlink radiocommunication service. Various techniques for selecting an optimal broadcast network, from a plurality of potential networks, are discussed. Parameters used in these selection techniques are estimated to reduce calculation complexity.

Description

SELECTION TECHNIQUES OF TRANSMISSION NETWORK FOR SYSTEMS OF HYBRID RADIOCOMMUNICATION THAT COMPRISES BOTH A SYSTEM OF CELLULAR COMMUNICATION AS A RADIODIUSION SYSTEM BACKGROUND OF THE INVENTION The present invention relates, in general terms, to radiocommunication systems and, more specifically to methods and systems for selecting a transmission network from which data is received in systems of this type.

The cell phone industry has advanced enormously in commercial operations in the United States of America as well as in the rest of the world. Growth in major metropolitan areas has far exceeded expectations and is rapidly exceeding the capacity of the systems. If this trend continues, the effects of this industry growth will soon reach even the smallest markets. Innovative solutions are required to meet these increased capacity needs as well as to maintain a high quality service and avoid raising prices. Throughout the world, an important step for the progress of radiocommunication systems is the change from analog to digital transmission. Another significant advance is the choice of an effective digital transmission scheme to implement the next generation technology. In addition, it is a widespread idea that the first generation of personal communication networks (PCNs) employ inexpensive pocket wireless phones that can be comfortably carried and used to make or receive calls at home, in the office, on the street , in the car, etc., will be provided, for example, by cellular companies that employ the digital cellular system infrastructure of the next generation. Important features desired in these new systems are a capacity to increase traffic and the ability to communicate at a much higher data rate than the data rates for which the current systems were designed. Today, access to channels in cellular systems is primarily achieved using the methods of multiple frequency division (FDMA) access and time division multiple access (TDMA). In FDMA, a communication channel is a unique radio frequency band in which a signal transmission energy is concentrated. Signals that may interfere with a communication channel include signals transmitted on adjacent channels (adjacent channel interference) and signals transmitted on the same channel on other cells (co-channel interference). Interference with adjacent channels is limited due to the use of band-pass filter that allows only the passage of signal energy within the specified frequency band. The co-channel interference is reduced to tolerable levels by restricting the reuse of channels by providing a minimum separation distance between cells in which the same frequency channel is used. Thus, with each channel receiving a different frequency, the capacity of the system is limited by the available frequencies as well as by the limitations imposed by the reuse of channels. The FDMA system was used to access channels in first generation systems such as, for example, AMPS. In TDMA systems, a channel consists, for example, of a time segment in a periodic series of time slots on the same frequency. Each period of time segments is known as a box. A given signal energy is limited to one of these time segments. An adjacent channel interference is limited by the use of a time gate or other synchronization element that allows the passage of only the received signal energy at the appropriate time. Thus, by assigning a different time segment to each channel, the capacity of the system is limited by the time segments available as well as by the limitations imposed by the reuse of channels in accordance with what is described above in relation to FDMA. As information technologies and communication technologies continue to move closer together, the demand for high data rate support (greater than 56 kbits / s) is growing rapidly particularly with the emergence of the Internet and the desire to transmit video information. The existing radio communication systems were not designed to handle such high data rates. One type of system that is considered to satisfy the demand for high data rates is a hybrid system in which high data rates are supported in the downlink (ie, in the direction of the base station to the mobile station) and lower data rate are supported in the uplink (i.e., in the direction of the mobile station to the base station). For example, it has been proposed that said hybrid system can be provided in which the cellular technology system is employed to support uplink traffic channels, low data rate downlink traffic channels, and control channels (uplink and downlink), while an emission transmission system is used to support high-speed data rate downlink traffic channels. Particularly, the transmission system known as the Digital Audio Broadcasting (DAB) system (digital audio broadcast) and specified in the European Telecommunication Standard entitled "Radio Broadcasting Systems"; Digital Audio Broadcasting (DAB) to mobile, portable and fixed receivers "(broadcasting systems, digital audio broadcast (DAB) to mobile, portable and fixed receivers), ETS 300401, February 1997, the disclosure of which is incorporated herein by reference, has been proposed for use in a hybrid system to support downlink channels of high data rates in combination with a cellular technology as specified in the pan-European GSM standard, broadcast systems, eg FM radio systems, They have been used independently of cellular systems for many years.Some emission systems such as those designed in accordance with DAB, are also simultaneous emission systems.In simultaneous emission systems, unlike cellular radio systems, the same information It is issued to remote units through several transmitters.The systems are useful for transmitting at high data rates. gone to its large bandwidth compared to cellular systems. However, by combining broadcast and cellular technologies, there are numerous design issues that must be resolved, in particular how a remote unit will be assigned to a broadcast network to begin receiving information on a high-speed data downlink channel. As is known to those skilled in the art, conventional cellular systems such as GSM and D-AMPS employ many different techniques to provide a combination of high traffic capacity and high quality of the received signal. For example, frequency reuse is a technique commonly used in these systems to improve capacity. This expression refers to the reuse of frequencies in cells separated by a sufficient distance (depending on other system design factors) in such a way that the interference of another channel caused by simultaneous transmissions on the same frequency does not create a signal quality received unacceptable in mobile stations. Another technique commonly employed in conventional cellular systems to help maintain a high quality of received signal is the use of mobile stations as measuring probes that evaluate the signal quality in the channels available for communication and provide reports to the system regarding the quality parameters measured. This information is then used by the cellular system for example to decide which channels should be used to establish new connections, as well as for the transfer of existing connections from one other cell (or within a cell). In conventional radio broadcasting / simultaneous transmission systems, on the other hand, the radio network is designed in such a way that all transmitters use a network to transmit the same information. Thus, a remote terminal simply tunes this frequency and listens to the transmitter or to the transmitters that are geographically closest. Therefore, unlike cellular systems, most broadcast systems have conventionally provided no mechanism for a remote station to select the network to which it will listen for downlink data. However, an FM broadcasting system (which includes a radio data service (RDS feature)) does not provide any mechanism for switching to an alternative frequency when the receiver is suffering from a poor received signal quality. In this system, the receiver simply switches to a predetermined frequency in the hope that it will continue to receive the same information issued with a better received signal quality. The receiver does not measure to identify a particular frequency for the switch nor does it know if an alternative frequency will in fact offer an acceptable received signal quality since switching. Thus, receivers operating in accordance with RSD may present what we know as a "ping-pong" effect as they switch back and forth between the two alternate frequencies until one of the frequencies provides an adequate received signal quality. In the proposed hybrid system described above, techniques for selecting a broadcasting system will be important, particularly since the broadcasting network that is closest geographically (as shown below) may not always provide the best signal quality received at the remote station. Thus, it would be desirable to provide new techniques for selecting a transmission network that overcomes the deficiencies of conventional systems. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to overcome the differences described above by providing techniques for selecting a transmission network offering optimum downlink signal quality for a particular connection. A further object of the present invention offers techniques that allow a remote station to select one of several possible broadcast networks from which information is received in a hybrid transmission / cellular radio communication network. In this document we describe several network selection techniques. These techniques employ one or more of the following parameters: total power received by the remote station, power received from interfering transmitters by the remote station, useful power received by the remote station and relationship between signal and interference, to identify an optimal transmission network for establish and / or transfer a call. BRIEF DESCRIPTION OF THE DRAWINGS These and other objects, features and advantages of the present invention will be readily apparent to a person skilled in the art from the following description, in combination with the drawings in which: Figure 1 illustrates a system of cellular radio communication / hybrid transmitter; Figure 2 shows a propagation of multiple trajectories in broadcasting transmission systems; Figure 3 illustrates an exemplary DAB box structure; Figure 4 is a block diagram representing an OFDM transmitter architecture; Figure 5 is a block diagram representing an OFDM receiver architecture; Figure 6 is a graph representing a weighting function used to describe the received signal power portion that is useful given the delayed OFDM signals; and Figure 7 illustrates simulation results for the received signal quality where each of the six exemplary DAB network selection techniques according to the present invention are tested and compared with a conventional technique. DETAILED DESCRIPTION OF THE INVENTION In the following description, for purposes of explanation and not limitation, specific details are raised such as particular circuits, circuit components, techniques, etc. In order to offer a thorough understanding of the invention. For example, various details are provided regarding exemplary modulation and transmission techniques. However, it will be apparent to one skilled in the art that the present invention can be practiced in other embodiments that depart from these specific details. In other cases, detailed descriptions of well-known methods, devices and circuits are omitted so as not to overload the description of the present invention with unnecessary details. An exemplary hybrid GSM / DAB radio communication system 100 is illustrated in Figure 1. As shown there, a geographic region served by the GSM system is subdivided into a number, n, of smaller radio coverage regions known as "llOa" cells. n, each cell having associated therewith, a respective base station 170a-n operating in accordance with the well-known GSM specification. Those skilled in the art will note that techniques and systems in accordance with the present invention for selecting a broadcast network can also be employed independently of such a cellular network or in a network. hybrid network where the cellular portion is designed in accordance with other standards. Each radio base station 170a-n has in association therewith a plurality of transmit and receive radio antennas 130a-n. Note that the use of hexagonal shaped cells 11Oa-n is employed as a graphically convenient way to illustrate radio coverage areas associated with a particular base station 170a-n. In fact, llOa-n cells can have irregular shapes, can be spliced, and are not necessarily contiguous. Each cell llOa-n can be subdivided in turn into sectors according to known methods. Distributed among the cells llOa-n is a number, m, of mobile stations 120a-n. In practical systems, the number, m, of mobile stations is much greater than the number, n, of cells. Base stations 170a-n comprise, inter alia, a plurality of base station transmitters and base transmission receivers (not shown) that offer two-way radio communication with mobile stations 120a-m located within their respective cells. As illustrated in Figure 1, the base stations 170a-n are connected to the mobile telephony switching office (MTSO) 150 which provides inter alia a connection to the public switched telephone network (PSTN) 160 and thus there is communication devices 180a-c. The cellular concept is known to those skilled in the art and therefore will not be described in greater detail here. In the hybrid system of Figure 1 there is also included a plurality of DAB networks for clarity of the figure, only two DAB 190a and 190b networks are represented graphically, or by circles of dots, even though more networks can be provided as necessary for provide the desired system capacity and considering other design criteria that will be easily understood by experts in the field. further, even though the circles of dots illustrated in Figure 1 are smaller than the hexagons used to represent them, the actual coverage area of each DAB network can obviously be smaller than that of each base station. Unlike cells 110a, 110b and 110c, however, each DAB network 190a and 190b will generally include several transmitters (although some DAB networks may have only one transmitter). The DAB networks 190a and 190b will preferably operate in different frequency bands to avoid interference between them. However, within each network the plurality of transmitters will transmit the same information in the same frequency band simultaneously. Thus, for example, if a mobile station 120m is assigned to the DAB network 190a for its downlink connection, the mobile station 120m can receive data from several transmitters within the DAB network 190a, depending on several factors such as the publication of the mobile station 120m, the transmission power of the DAB network, etc. This concept is illustrated in figure 2.

Here, a remote station 200 is receiving signals from each of the four DAB transmitters 210a, 210b, 210c and 210d. According to the radio propagation path between the transmitters and the remote station, the remote station can receive one or more signal paths (echoes) from each transmitter, as conceptually illustrated through the two illustrated paths received from the transmitter 210d. The propagation of multiple paths and reception of signals associated with the use of a transmission network to transmit both to the remote station is also significant as a factor in considering which network to select as will be discussed in more detail later. In the exemplary embodiments described herein, DAB networks are employed to provide high-speed downlink data up to the remote stations. To provide a complete understanding of the techniques for selecting between transmission networks for e.g. purposes of initially allocating a traffic and transfer channel, a basic description of the DAB signal transmission is first provided, followed by exemplary signal quality measurements received. The interested reader can find more detailed information regarding the DAB signal transmissions in the ETSI standard incorporated above by reference. The frame structure of an exemplary DAB signal is illustrated in Figure 3. There it can be seen that each frame includes three fields. The first field 300 contains a synchronization word (sync), which is used by the remote unit to synchronize the transmitted signal. In this case, the synchronization word comprises two symbols. The second field 310 is the Quick Information Channel (FIC) employing n symbols to provide information regarding the current configuration of the Main Service Channel (MSC) 320. The main service channel 320 contains m payload data symbols. In the DAB system, this frame structure is transmitted using several OFDM signals (multiple option by orthogonal frequency division). In an OFDM scan, the bandwidth is divided into a large number of orthogonal narrow band sub-channels that are transmitted in parallel. In OFDM schemes, a data stream of high data rate is modulated in a large number of these channels. Even though the speed of the data stream is quite high, the modulation speed of each sub-channel is relatively low, which makes each symbol relatively long. This, in turn, makes the OFDM symbols more resistant to the effects of the propagation of multiple trajectories that are problematic in transmission systems. In addition, an additional protection interval (an extension in time of the OFDM signal) is inserted between consecutive OFDM signals, thus further reducing the effects of the delay extension. The signals in different sub-channels are orthogonal in the time domain but are spliced in the frequency domain. More specifically, an OFDM signal can be defined with the following equation: x (t) - o = t = r + r where Ptx is the transmitted power, N is the number of carriers, D * is the information about the carrier k, T is the duration of a symbol and Tg is a protection interval. So, an OFDM signal is transmitted for T + T? seconds. Figure 4 illustrates a block diagram representation of an OFDM mentioned transmitter that can be employed to implement the present invention. There, the data stream of high data rate to be transmitted is first modulated in baseband in block 400. The modulated data is then separated into the desired number of sub-channels by means of serial to parallel converter 410. Each sub -channel is then converted upwardly to its assigned radio frequency in multipliers 420. Next, each sub-channel is multiplexed together to form a composite signal x (t) for transmission. The reverse process is applied in each remote station receiver as illustrated in Figure 5. The received composite signal is (t) is correlated with each sub-channel frequency in blocks 500 and 510 to extract each sub-channel from the composite signal After, a parallel to serial converter extracts the data stream in parallel in block 520. Finally, a symbol estimation is carried out in block 530 to decode the received information symbols. Alternative implementations of OFDM transmitters and receivers can be designed using fast inverse Fourier transformation techniques and fast Fourier transformation, respectively. In DAB systems, the synchronization field 300 in each frame is transmitted using two OFDM channels. A sub-channel carries a NULL signal that is used by the receiver for an approximate synchronization of time. The second OFDM sub-channel is used as a reference to demodulate the received signal which, in accordance with this exemplary embodiment, is modulated using a differential modulation scheme, such as differential phase quadrature change manipulation (DQPSK). As mentioned above, there are several differences between DAB radio networks and conventional cellular radio networks that need to be taken into account when determining how to measure the selection criteria for DAB networks. Specifically, the simultaneous transmission of DAB systems creates an artificial delay extension and a remote station will experience delayed FDM signals that can splice the receiver detection window thus causing interference. When a signal is substantially delayed, it not only occurs in inter-symbol interference (ISI), but also inter-channel interference due to losses in orthogonality between sub-channels. This type of interference is often referred to as high interference, since the network itself generates its own interference. Thus, the relationship between signal and interference (SIR) in a receiver depends on the structure of the network configuration (that is, the propagation delays). A SIR measurement in DAB networks can be obtained in accordance with the following formula: ! * =. ST * P Q (t. »* R + p + N. SF-t * / &l-β < t. -« > >) + L + N0 considering that all Nj and transmitters within the DABj network are transmitting on all sub-channels simultaneously. The total received power (including slow fading) of the transmitter and which belongs to the DABj network is indicated by Pj ±, the self-interference associated with transmissions from transmitters in the network j is indicated by P3auto and QO is a weighting function that describes the fraction of the total received power that may be useful due to the delayed OFDM signals. This weighting function is illustrated in Figure 6. The difference between the signal arriving and the time when the receiver begins to detect the signal is indicated as follows ti-tr. The interference of others. DAB networks are. provided by Pjext and the noise level is indicated by N0. In accordance with the present invention, the remote station measures the received signal quality associated with each different DAB network that can receive or those identified for measurement in the control channel transmitted by the base station in the GTM portion of the hybrid system. This information can then be used to select one of the DAB networks to support the connection, this decision can be taken either at the remote station or by the system if quality measurements are reported. SIR is a parameter that can be estimated and used as a basis for network selection. However, in accordance with other exemplary embodiments, other measurements may also be employed, since the SIR estimate may be relatively complex. Six exemplary network selection schemes are described below, where a DABj network is selected from among a set of possible networks (for example, the seven geographically closest networks). In the methods described below, it is considered that the received power is much greater than the noise floor, that is, the noise floor N0 / is omitted: Method I Method II Method III Method IV argmaxl Method V ar. ax (PM /) =, Method VI arg. ax (5XR /) - w Methods I and V select the DAB network from which the terminal experiences the highest total received power and the highest useful received power, respectively. Method II selects the DAB network with the highest total received power including external interference. Methods III, IV and VI are based on SIR. These methods vary in terms of calculation complexity. For example, method I requires only one estimate of Pji, while methods II-IV also requires an additional estimation of parameter Pjext. The methods V and Vi add even more complexity since they require an additional estimate of the relative propagation delays (ti-tr) between the received signals. The applicant has simulated each of these exemplary modalities to determine their effectiveness in selecting among the DAB networks. The results of this simulation are presented in the graph of Figure 7, which presents the function of cumulative distribution (cdf) versus the relationship between signal and interference (SIR) for each approach. The graph shows the results of the six exemplary modalities (even though the resolution of the graph is such that the results of the simulation of methods I and V and III, IV and VI, respectively, are essentially linked together), and for For purposes of comparison, the results are also presented for a system in which the terminal is always connected to the nearest DAB network geographically (dotted line). Note that method II provides a relatively poor performance compared to the selection of the closest DAB network, so the other techniques all provide better performance. Methods III, IV and VI (based on SIR) provide better performance. Following are techniques according to the present invention for estimating the parameters required to employ the selection criteria described above. One consideration used to create these estimation techniques is that, for remote stations currently connected to the system (ie, they have received a downlink traffic channel), the measurements do not interfere with the reception of data. Accordingly, the DAB receiver makes no estimate when the FIC and MSC blocks are received, except for the receiver's own signal. Instead, the DAB receiver uses the period of time in which the NULL signal is received to make measurements used to estimate the selection criteria. During NULL, the receiver jumps to an alternate frequency of another DAB network (a list of one or more alternative frequencies can be provided in the FIC and / or can be transmitted in the control channel through the cellular portion of the hybrid system) and make an estimate. After the expiration of the period of the NULL symbol, the receiver jumps back to the frequency at which its current DAB network is transmitting and continues to detect its data. To obtain estimates of the quality of the signal received in your. current frequency, the receiver can simultaneously detect / decode its received data and apply one of the aforementioned estimation schemes. The estimation of the parameters used in the selection criteria is less complicated if the different DAB networks have synchronized transmissions. Then, several of the proposed estimation schemes use knowledge of the signal structure NULL DAB (symbol) to simplify the calculations. More specifically, the NULL signal is a special OFDM signal that each transmitter within a DAB network transmits only in one of the sub-channels. A unique pattern is assigned to each transmitter consisting of a set of sub-channel pairs indicated as: «H (k¡, k¡ + l),. . . , (k¡, k? + l) In this context, a pair refers to two adjacent sub-channels separated in frequency with 1 / T. This construction of the NULL signals combined with a long protection interval reduces the auto interference and the external interference between the sub-channels in the NULL signal. So the sub-channels do not experience the SIR in accordance with what is described above. Instead of this, the output received after the correlation in a super-channel k may be approximately the following:. . . . . rk. mu. * Ht. NULL pt Dk. frvLL + nk. ma where Dk, NUL is data transmitted in the sub-channel k, Pji includes all the received powers, H ^ NUL is a complex path gain (channel) that includes fast fading and? JC, NUL is a totally white Gaussian noise ( AWGN). Then / for the methods described above that employ Pj? in the selection algorithm, this parameter can be estimated as: ? l. HÜtL? where c (M? j) is the number of elements in the set M? j, that is, the cardinal number of the set. In the case of methods described above using Pje? T in the selection algorithm, the same equation can be used as for Pj? above, but for sub-channels transmitted by external interference transmitters, that is, other 'DAB networks. In the case of the methods described above, where Pjtot is used in the selection algorithm Pj? and Pjext can be calculated according to what is described to provide Pjt0f However, in the case of the received frequency band, it is possible to obtain a better estimate of the total power received by: N-l. 2c ( { FIC, MSC)) 4e. { Fic S. sq kS -o "*.« ' where the set between. { FIC, MSC} they are all (or a subset) the OFDM symbols that are not used in the synchronization field as shown in figure 3. To obtain an estimate of the time difference ti-tr used, for example, in methods V and VI described above, it is possible to employ any known technique to estimate the difference between the arrival time of the received signal and the time in which the receiver begins to detect the signal. For example, the channel correlation between two adjacent sub-channels is often very high with only a small phase shift that depends on the sub-channel separation and ti-tr. This correlation can be expressed as: R * The ** \ H * vP f ^^ T ak. ÜLLak -I, NVLL I ak. UILI where * is a complex conjugate. Thus, ti-tr can be estimated as: < t, - * r > -? ? r (rt> NU (k.k + Deu? 2 c IM¡) 2p LLrk-l.lfULL *) The selection of a particular network can then be carried out by inserting the estimated parameters according to the described above in one or more of the I-VI selection algorithms described above to determine an optimal network for providing a downlink service to a remote station. In the case of systems in which transmitters between DAB networks transmit asynchronously, there are no periods during which the remote station can safely make measurements on other DAB network frequencies without losing MSC or FIC data. Then the receiver can not measure the useful and interference powers in accordance with what is described above for insertion in the selection algorithms. However, it is possible to obtain an estimate by measuring the total received power: N-l • tot Nk > k * .f ' and method II can then be employed. Thus, methods in accordance with the present invention implement the capability in radio systems also provide high data rates in the downlink. The results of the simulation described here indicate that methods III, IV and VI provide a very good coverage, even in the case of very dense networks, at a relatively low frequency reuse factor. The estimation of the parameters used in these methods can be carried out using the existing DAB signal structure. A) Yes, selection schemes in accordance with the present invention offer the additional benefit that they do not require any additional equipment and that they are easily implemented in programmatic. The methods of the present invention can be used not only in the initial establishment of a connection but also during transfer procedures. For example, the estimated value in SIR is of importance to detect when it is time to carry out a transfer. Thus, the methods discussed here will also provide network selection schemes that can be employed during a transfer. The present invention has been described in terms of specific modalities to facilitate understanding. The above modalities, however, are illustrative and not restrictive. It will be readily apparent to one skilled in the art that one can leave the specific embodiments illustrated above without departing from the spirit or scope of the present invention. Accordingly, the invention should not be considered as limited to the foregoing examples, but should be considered, in terms of its scope, in accordance with the following claims including their equivalents. highest total received power. The hybrid radio communication system according to claim 1, wherein said device for evaluating determines a total useful power received by said remote station from each of said transmission networks and selects a transmission network associated with the highest total useful received power. . The hybrid radio communication system according to claim 3, wherein said total power includes powers associated with signals from interfering transmitters. The hybrid radio communication system according to claim 1, wherein said device for evaluating determines a signal to interference ratio (SIR) associated with signals received by said remote station from each of said various transmission networks and selects a transmission network. associated with a higher SIR. The hybrid radio communication system according to claim 1, wherein said device for evaluating determines a relationship between a total power received by said remote station from each of said various transmission networks and said total power plus the power of interfering transmitters and select a transmission network associated with a higher ratio.

The hybrid radio communication system according to claim 1, wherein said device for evaluating determines a relationship between a total power received by said remote station from each of said several transmission networks and a power received by said remote station from of transmitters that interfere and selects a transmission network associated with a higher ratio. The hybrid radio communication system according to claim 1, wherein said plural networks transmit synchronously. The hybrid radio communication system according to claim 9, wherein said evaluating device carries out measurements during a period in which synchronization symbols are transmitted. The hybrid radio communication system according to claim 1, wherein said plural networks transmit asynchronously. A method for selecting one of several transmission networks for transmitting data to a remote station, comprising the steps of: transmitting data from each of said various transmission networks employing an orthogonal frequency division multiplexing; evaluate in a remote station, each of said transmission networks using a selection algorithm; and selecting one of said several transmission networks based on an output of said selection algorithms. The method according to claim 12, wherein said evaluation step further comprises the step of: determining a total power received by said remote station from each of said various transmission networks and selecting a transmission network associated with a higher total received power. The method according to claim 12, wherein said evaluating step further comprises the step of: determining a total useful power received by said remote station from each of said various transmission networks and selecting an associated transmission network with a higher total useful received power.

. The method according to claim 13, wherein said total power includes powers associated with transmitter signals that interfere. 16. The method according to claim 12, wherein said evaluating step further comprises the step of: determining a signal-to-interference ratio (SIR) associated with signals received by said remote station from each of said various networks of transmission and select a transmission network associated with a higher SIR. 17. The method according to claim 12, wherein said evaluating step further comprises the step of: determining a relation between a total power received by said remote station from each of said several transmission networks and said total power plus the power of transmitters that interfere and select a transmission network associated with a higher ratio. 18. The method according to claim 12, wherein said evaluation step further comprises the step of: determining a relationship between a total power received by said remote station from each of said various transmission networks and the power received by said remote station from interfering transmitters and Select a transmission network associated with a higher ratio. 19. The method according to claim 12, further comprising the step of: transmitting data synchronously between said plurality of transmission networks. The method according to claim 19, wherein said evaluating step further comprises the step of: making estimates of said various transmission networks when synchronization symbols are being transmitted. The method according to claim 12, further comprising the step of: transmitting data asynchronously between said various transmission networks.

Claims (1)

1. 28 CLAIMS A hybrid communication system comprising: a plurality of cellular radio transceivers to support data communications with a remote station, each radio transceiver is associated with a cell; a plurality of transmission networks for supporting downlink data communications with said remote station, each transmission network operates on a different frequency and each transmission network has at least one transmitter for transmitting data on a respective frequency associated with this network. transmission; and a device for evaluating each of the various transmission networks and selecting one of said several transmission networks to provide said downlink data communication with said remote station. The hybrid radio communication system according to claim 1, wherein said at least one transmitter transmits signals by the use of an orthogonal frequency division multiplexing. The hybrid radio communication system according to claim 1, wherein said device for evaluating determines a total power received by said remote station from each of said transmission networks and selects a transmission network associated by the