MXPA99006087A - Method and apparatus for providing high speed services using a wireless communications system - Google Patents

Abstract

A method and apparatus for scheduling transmissions between a plurality of communications sites within a communications system. The communications system provides service to a service area which is divided into sectors. Each sector is assigned at time subframe in a pattern where adjacent sectors use different subframes. Communications sites within each sector communicate packets of information in at least one time subframe according to a schedule to minimize interference from other communications sites.

Description

METHOD AND APPARATUS FOR PROVIDING HIGH SPEED SERVICES USING AN INAL MBRICO COMMUNICATION SYSTEM BACKGROUND OF THE INVENTION The invention relates generally to wireless communication system. More particularly, the invention relates to the provision of high-speed broadband services to a large number of users using a minimum amount of bandwidth in a wireless communication system. The need for high-speed broadband packet services will grow tremendously in the coming years as work at home, telecommunications and Internet access become increasingly popular. Customers are expecting high quality, reliability and easy access to high-speed communications from their homes and small businesses. Data rates of at least 10 mega-bits per second (Mbps) are required to provide high-speed services to: a) have access to the World Wide Web (WWW) for information and entertainment, b) provide speeds of data comparable to local area networks (LAN) so that telecommunicators have access to their computer equipment and data in the office, and c) multiple media services such as voice, image and video. REF .: 30572 Traditional wireless telecommunication systems have the problem of providing high-speed services due to the amount of bandwidth that these services require. Bandwidth is a key limiting factor in determining the amount of information that a system can transmit to a user at any time. In terms of wireless networks, the bandwidth refers to the difference between two limiting frequencies of a band expressed in Hertz (Hz). The concept of bandwidth can be better understood using an analogy. If the information transported by a network was water, and the links between the communication sites were tubes, the amount of water (ie, information) from one network could transmit from one site to another site would be limited by the speed of water and the diameter of the tubes that transport the water. Ignoring speed for a moment, the larger the diameter of the pipe, the greater amount of water (ie, information) can be transmitted from one site to another in a given time interval. Similarly, the more bandwidth a communication system has available, the more information it can carry. Traditional wired communication systems use modems and a physical transmission medium such as a double twisted conductor copper wire can not achieve the data rates necessary to provide high speed service due to bandwidth limitations (ie, tubes little ones) . In an attempt to solve this bandwidth problem, the local central companies (LEC) have been planning and installing fiber / coaxial hybrid (HFC) and digital switched video (SDV) networks. Those wired networking methods to provide high-speed access, however, require substantial market penetration to keep subscriber costs at an acceptable level due to the high costs involved. Similarly, traditional wireless systems such as Narrowband and Personal Cellular Communication Services (PCS) are limited bandwidth as well. As an alternative, wireless solutions such as Multiple Channel Multiple Point Distribution Service (MMDS) and Local Multiple Channel Distribution Service (LMDS) have become attractive for scenarios of a low percentage of query, for example, a market penetration of a low percentage. The benefits of wireless systems for providing high-speed services are that they can be deployed quickly without the installation of local wired distribution networks. The problem with the MMDS and the LMDS, however, is that these solutions so far offer a limited uplink capacity. In addition, these solutions may not be able to support a large number of users due to the limited reuse of the frequency. One solution to solve the bandwidth limitation problem for those wireless systems is to maximize the available bandwidth through the reuse of the frequency. The reuse of the frequency refers to reusing a common frequency band in different cells within the system. The concept of reusing the frequency will be discussed in more detail with reference to FIGURES 1 and 2. FIGURE 1 is a diagram of a typical wireless communication system. A typical wireless communication system includes a plurality of communication sites, such as a mobile telephone switching office (MTSO), base stations, terminal stations, or any other site equipped with a radio transmitter and / or receiver. FIGURE 1 shows a base station 20 in communication with terminal stations 22. The base station 20 is usually connected to a fixed network, such as the PSTN or the Internet. Station 20 could also be connected to other base stations, or connected to an MTSO in the case of mobile systems. The terminal stations 22 may be fixed or mobile.

The base station 20 communicates information to the terminal stations 22 using radio signals transmitted over a range of carrier frequencies. The frequencies represent a finite natural resource, and are under extremely high demand. In addition, the frequencies are heavily regulated by the Federal and State governments. Consequently, each cellular system has access to a very limited number of frequencies. Consequently, wireless systems aim to reuse frequencies in as many cells within the system as possible. To achieve this, a cellular system uses a frequency reuse pattern. A major factor in the design of a frequency reuse pattern is to try to maximize the capacity of the system while maintaining an acceptable signal-to-interference (SIR) ratio. SIR refers to the ratio of the level of the desired signal received to the level of the undesired signal received. Co-channel interference is interference due to the common use of the same frequency band by two different cells. To determine frequency reuse, a cellular system takes the total frequency spectrum assigned to the system and divides this into K frequency reuse patterns. FIGURES 2 (A) through 2 (D) illustrate examples of frequency reuse patterns of K = 4, 7, 12 and 19.

As shown in FIGURES 2 (A) through 2 (D), a cellular communication system has a number of communication sites located through a geographical coverage area served by the system. This geographical area is organized into cells and / or sectors, with each cell typically containing a plurality of communication sites such as a base station and terminal stations. A cell is represented in FIGURES 2 (A) through 2 (D) as a hexagon. FIGURE 2 (A) shows a frequency reuse pattern where K = 4. The cells are grouped into sets of four, with each set using frequency bands 1 through 4. This group of four cells is then repeated until it is cover the entire service area. This same pattern is shown in FIGURES 2 (B), 2 (C) and 2 (D) for sets of 7, 12 and 19 cells, respectively. Thus, in essence, the pattern of frequency reuse represents that such geographic distance can be maintained between cells using common frequency bands so that the co-channel interference for those cells remains low at a given threshold to ensure the successful reception of the signal. The most aggressive frequency reuse pattern for cellular systems is where K = 1. Under this pattern, the same frequency band can be reused in each cell in the cellular communication system. In typical narrowband cellular systems, the total amount of the frequency spectrum available to a system is divided by K. This determines how much frequency is available for a particular cell. For example, if a cellular system was assigned 20 megahertz (MHZ) of spectrum, and the frequency reuse pattern is K = 4, then each cell has a value of 5 MHz of frequency over which to transmit radio signals. If K = 1, the entire 20 MHZ value of the frequency spectrum is available for each cell to transmit information potentially. To better understand the magnitude of the benefits given by the frequency reuse pattern of K = 1 discussed in the previous example, the figures will be used for a real communication system. The frequency assignment for mobile cellular systems in the United States is 824-829 MHZ and 869-894 MHZ for a given service area. Since each service area is served by two cellular network operators, each cellular system must divide the available bandwidth for the given service area. This contributes to a total of 25 MHZ of available bandwidth per system, and 12.5 MHZ being used to transmit from a base station to a terminal station (referred to as the downlink), and 12.5 MHZ being used to transmit from the terminal station to the base station (what is done reference as the uplink). The typical American mobile cellular system has a frequency reuse pattern of K = 21. Thus, each cell has approximately 1.2 MHZ (25 MHZ divided by 21) of spectrum to transmit information. If a frequency reuse pattern of K = 1 could be established, all 25 MHZ would be available to transmit information for each cell. This results in a 21-fold increase in the frequency spectrum available for each cell. Using the analogy again, the diameter of the pipe is increased 21 times. Several currently existing systems employ frequency reuse patterns of K = 1. One example includes cellular systems that employ code division multiple access (CDMA). CDMA systems broadcast the transmitted signal through a wide frequency band using a code. The same code is used to recover the signal transmitted through the CDMA receiver. CDMA systems reuse the same frequencies from cell to cell. CDMA systems, however, require a large amount of frequency spectrum. In addition, the amount of spectrum required by CDMA systems to offer high-speed broadband services to a large number of users is commercially unrealistic.

Another example of aggressive frequency reuse includes cellular systems employing time division multiple access (TDMA), an example of which is described in U.S. Patent Number 5,355,367. The system discussed in U.S. Patent No. 5,355,367 is a TDMA system that uses redundant transmission of information packets to ensure a proper SIR for a call. The use of redundant packet transmissions, however, only exchanges one inefficiency for another. Although a frequency band can be reused from cell to cell, the transmission of redundant packets means that a smaller portion of that frequency band is now available to be used by each cell in the system, since multiple packets are required to ensure the successful reception of a single package. In addition to the problem of frequency reuse, traditional cellular systems are not designed to allow a communication site to use all the available bandwidth for the system ("total system bandwidth"), due to the low speed of the system. data expected by users. Instead, traditional cellular systems employ various techniques in both the frequency domain and the time domain to maximize the number of users able to be served by the system. These techniques preach or allocate smaller portions of the total system bandwidth to the service of individual communication sites. Those smaller portions are able to provide enough bandwidth to offer high-speed services. An example of a technique used in the frequency domain is Frequency Division Multiple Access (FDMA). The FDMA divides the available bandwidth into smaller sections of bandwidth under the concept of providing less bandwidth for a number of users. Using the analogy, a single large tube is separated into a number of smaller tubes, each of which is assigned a sector or cell. Unfortunately, the drawback is that these smaller frequency bands are not large enough to support high-speed bandwidth packet services. Furthermore, by definition, a communication site is not capable of using the total bandwidth of the system, but is limited to a discrete portion of the total system bandwidth. An example of a technique used in the time domain is TDMA. The TDMA divides the available bandwidth into discrete time sections, and allocates each time section (typically known as a time slot) to each communication site. Each communication site transmits and receives information only in the specific time interval of the site, thus avoiding collisions between the communication sites. Using the analogy, each cell or sector has access to the entire tube for a certain amount of time. Traditional TDMA systems, however, are designed to handle circuit switching and, therefore, are static in nature. These systems assign a specific time interval of a fixed duration for a specific communication site for the entire duration of a call. As a result, a communication site can not transmit more information than can be accommodated by this allocated time slot. In any case, those traditional TDMA systems are not designed to take advantage of the new switching technology, such as packet switching. In some systems, a combination of FDMA and TDMA is used to improve the system's call capacity. These FDMA / TDMA systems, however, only combine the disadvantages of both. In addition, the FDMA / TDMA systems do not allow the user to access the total bandwidth of the system on a dynamic basis. To solve this problem, some TDMA systems employ a concept called "dynamic allocation of resources" to share radio resources between communication sites efficiently. Methods of dynamic allocation of resources, however, require a central controller or complicated algorithms to dynamically determine the time intervals available and coordinate their use. In addition to the above, it can be seen that there is a substantial need for a system employing a frequency reuse pattern of K = 1 which allows both a communication site to use the total bandwidth of the system on a dynamic basis, thus providing high-speed broadband packet services to a large number of users and at the same time reducing the amount of bandwidth required.

BRIEF DESCRIPTION OF THE INVENTION This need and other needs are met using a method and apparatus for programming transmissions between a plurality of communication sites within a communication system. The communication system provides service to a service area which is divided into sectors. Each sector is assigned a subframe of time in a pattern where the adjacent sectors use different sub-frames. The communication sites within each sector communicate information packets in at least one subframe of time according to a program to minimize the interference of other communication sites.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 shows a block diagram of a typical wireless system. FIGURE 2 (A) shows a frequency reuse pattern when K = 4. FIGURE 2 (B) shows a frequency reuse pattern when K = 7. FIGURE 2 (C) shows a frequency reuse pattern when K = 12. FIGURE 2 (D) shows a frequency reuse pattern when K = 19. FIGURE 3 is a cell map with arrows' indicating the main sources of interference for a downlink transmission for a shaded sector within a cell. FIGURE 4 is a cell map with arrows indicating the main sources of interference for an uplink transmission for a shaded sector within one. cell. FIGURE 5 is a cellular map with each cell divided into six sectors using two sub-frames according to a first embodiment of the invention. FIGURE 6 is a diagram illustrating a left-to-right protocol according to a second embodiment of the invention.

FIGURE 7 is a cell map with each cell divided into six sectors using six sub-frames according to a third embodiment of the invention. FIGURE 8 is a diagram illustrating a stacked resource allocation protocol according to a fourth embodiment of the invention. FIGURE 9 is a normalized movement graph vs. aggregate charge normalized according to a fourth embodiment of the invention.

DETAILED DESCRIPTION In accordance with the present invention, a method and an apparatus are discussed to provide a frequency reuse pattern of K = 1 for a wireless communication system, which allows each communication site within a sector to use all the bandwidth available to the system on a dynamic basis. A cellular communication system is an example of a system that falls within the scope of the present invention. The embodiments of the invention use a TDMA system design so that each cell and sector of the system can use a common frequency. The modalities illustrated here identify the worst sources of interference for downlink and uplink transmission and reception between communication sites within a cell. Through the use of directional antennas, cellular sectorization and a programming algorithm, these modalities avoid the main sources of interference for a communication site within the system. This reduces the co-channel interference for the successful reception of radio signals at the point where all the available band frequencies of the system can be reused from cell to cell, and for each communication site on a dynamic basis. In the context of this description and the appended claims to the present, any reference to programming can be implemented using a programmer, and sufficient memory to store the programming algorithm. A programmer includes a processing unit with sufficient processing speed. Examples of processing units include a microprocessor used in a general-purpose computer or network server, and also a dedicated physical component devicespecial. In addition, any reference to the communication of information includes transmitting and / or receiving the information. To illustrate various embodiments of the invention, assume a packet-switched TDMA wireless network of fixed (ie non-mobile) bandwidth with user data rates of 10 Mbps, link lengths typically less than 10 kilometers, and operating frequencies. in the range of 1 to 5 giga-hertz (GHz). To support a user data rate of 10 Mbps, a system uses a bandwidth of approximately 10 MHz. It is worth noting that although different modalities are discussed in accordance with a fixed network, a mobile network falls within the scope of the invention as well. The TDMA system is organized as follows. Each cell is divided into multiple sectors, each of which is covered by a colocalized directional antenna with a base station in the center of the cell. The terminal stations also use directional antennas directed to their respective base station antennas. The beam width (angle) of each antenna of the base station should be wide enough to cover the entire sector, while an antenna of the terminal station pointing to a designated base station antenna may have a smaller beam width for reduce the interference. The lobular gain ratios from front to back ("FTB ratio") for the antennas of the base station and the terminal station may be different, and are assumed to be finite. The time is divided so that the information packet can be transmitted in each interval. In addition, the downlink and the uplink between the end stations and the base stations can be provided by duplex time division (TDD) using the same radio spectrum, or division by duplex frequency (FDD). More specifically, each cell is divided into six sectors, each of which is served by an antenna of the base station with a beam width of 60 degrees. The antennas of the terminal station may have an angle less than 60 degrees. Even for this advantageous structure, the optimal programming of packet transmissions is complex, which is known by mathematicians as a complete NP problem. Therefore, the different embodiments of the invention use a heuristic method to identify and avoid the main sources of interference. FIGURE 3 is a cell map with dates indicating the main sources of interference of a downlink transmission for a shaded sector within a cell. Using the trajectory loss model, it is found that the main interference for the downlink of the shaded sector comes from sectors of the same cells and sectors of other cells. Specifically, as shown in FIGURE 3, the alignment sector (A) and the opposite sector (B) are the main sources of intercell interference. Sector (A) is a main source of intercell interference because an antenna of the terminal station in the shaded sector while pointing to its base station antenna also sees the front lobe of the base station antenna for the sector ( TO) . Similarly, Sector (B) is another main source of intercell interference due to its short distance from the shaded sector. FIGURE 4 is a cell map with arrows indicating the worst sources of interference for an uplink transmission for a shaded sector within a cell. Similar to the downlink map shown in FIGURE 3, the main interference source for the uplink is received in the sectors in the same cell and other cells. For downlink and uplink, the interference is compensated in-part by using directional antennas at the base station. Directional antennas limit the interference received from the neighboring cells due to the FTB ratio of the directional antennas and the distance between the sources of intercell interference and the antenna of the receiving base station located in the shaded sector. FIGURE 5 is a cellular map with each cell divided into six sectors and two subframes (for a downlink or uplink transmission) according to a first embodiment of the invention. The total amount of bandwidth available to the system is separated into a fixed number of time slots for a downlink or uplink. The subframes of time shown in FIGURE 5 are used to illustrate either the uplink or the downlink, but not both simultaneously. The time intervals used for a downlink or an uplink are grouped into sub-frames. The consecutive sub-boxes are marked alternately by 1 and 2. The sectors are also marked by 1 and 2, so that the non-adjacent sectors share the same mark. The sectors with the i mark can program the transmission of packets in time intervals of the sub-panel i. As a result, each sector can transmit in a 50% work cycle, consuming at most half of the total bandwidth. The term "adjacent sectors" as used herein means a sector which shares a common limit with another sector, with the limits being defined in the different embodiments of the invention as three lines comprising a sector of a cell in the form of a hexagon. A point that is necessarily formed from the union of any of two of the following limit lines is not considered a limit for any of the different embodiments of the invention described herein. Similarly, although a cell is typically represented as a hexagon to facilitate the theoretical construction of a cell pattern, it can be seen that the actual implementation of a cellular system creates boundaries that do not necessarily follow precisely the theoretical pattern. Consequently, any reference to a common limit refers to the limits taken using the theoretical pattern, not the actual implementation. Notwithstanding the above, any limit line contemplated and used in the theoretical pattern falls within the meaning of the term limit as used here. A method for providing system operation for the time slot allocation scheme discussed with reference to FIGURE 5 is for a sector to appropriate time slots of other subframes. This method does not increase the total capacity of the system for a uniform traffic load, but allows efficient sharing of the bandwidth, especially when transient traffic loads arise. The loan of time intervals from other sub-frames used by neighboring sectors, however, requires a central or central information and coordination controller between the base stations, which significantly increases the course and complexity of the system. A better method to improve the operation of the system for this allocation scheme is to allow the use of intervals in a subframe not originally assigned to a given sector. A protocol is applied from left to right to minimize concurrent transmissions, thereby reducing interference. FIGURE 6 is a diagram illustrating a left-to-right protocol according to a second embodiment of the invention. A programmer schedules when a communication site will transmit information in a sub-frame to avoid the main sources of interference from other communication sites. The programmer does this using the protocol from left to right. According to the protocol from left to right, the programmer creates two transmission programs. The first transmission program is known as the original transmission program. The second transmission program is known as the excess transmission program. According to the original transmission program, the communication sites within the sectors marked 1 are programmed to transmit packets at time intervals starting from the left side of subframe 1, or instead from ti to t2. Communication sites within the sectors marked as 2, however, are programmed to transmit at time intervals starting from the right side of subchart 2, or instead from t3 to t2. In this way, it can be seen that the protocol from left to right alternates from the side that is a communication site to transmit information in its assigned sub-frame. It is worth noting that the terms left side and right side as used here correspond to the start and end times for a subframe of time. The terms left side and right side are therefore used here to denote temporal references, not spatial references. If the information for the sectors marked as 1 exceeds the amount of information capable of being transmitted in sub-box 1, the protocol from left to right creates a program of excess information. The protocol from left to right dynamically programs the excess of information from sub-box 1 for the transmission in sub-box 2 on the left side of sub-box 2, that is, from t2 to t3. The excess of information in sub-section 2 is programmed to be transmitted in sub-box 1 on the right side of sub-panel 1, ie from t2 to you. Since the protocol from left to right programs the transmission of excess information in opposite directions of the original transmission program for a subframe, the collision probabilities are reduced to a minimum. As illustrated above, the term "information excess" is used to describe the information generated from a communication site within a sector which exceeds the amount of information that can be transmitted in the subframe of time originally assigned to the sector. The term excess information does not refer to information that is unnecessary or superfluous. Depending on the traffic load, the protocol from left to right produces three to six concurrent packet transmissions in each time slot per cell side. Ideally, all sectors in a cell can transmit simultaneously, thereby producing a sector reuse factor of one in each sector of each cell. Of course, if concurrent packet transmissions result in an unsuccessful reception, the system simply retransmits the information using any conventional retransmission scheme. By programming the excess information from a sub-frame to another sub-frame within the same cell, a communication site within a sector can dynamically access an additional bandwidth on demand. Since this embodiment of the invention uses packet switching instead of circuit switching, this mode does not maintain a fixed correspondence between the time intervals within a subframe and the communication sites. Instead, this embodiment of the invention dynamically allocates time intervals within a sub-frame according to the amount of information to be transmitted by the communication sites. The protocol from left to right takes advantage of the fact that it is unlikely that each communication site located through the cell will operate at full capacity at the same time. A more likely scenario is that, for example, a terminal station will have access to the Internet to connect to a video conference or view the latest news report, while another is simply reading texts based on email. Thus, since terminal stations will vary their bandwidth needs at any given time, the left-to-right protocol implements a method which takes advantage of the subframes for sectors with terminal stations that are less active, using a scheme which minimizes the probability of collisions between sectors. For example, if a base station has 10 information time slots to be transmitted to a terminal station, the system dynamically assigns 10 time slots to accommodate the transmission. Similarly, if a base station has only 2 information time slots, only 2 time slots are assigned by the system. Accordingly, if a communication site or a plurality of communication sites within that sector are engaged in bandwidth intensive activities with the point at all time intervals within a subframe of the initial sector are used, the system may use another sub-section of the sector to transmit the excess information. The system will select another subframe originally programmed to fill its sub-frame on the opposite side of the initial sub-frame. In this way, assuming that the entire overflow capacity of the subframe is not being used by its corresponding sector, the risk of collisions due to interference is minimized. In the case of collisions, the system simply transmits the information using any traditional retransmission scheme. It is important to note that although the protocol from left to right was illustrated here using a cell comparison six sectors and two subframes, it can be seen that any combination of sectors and subframes falls within the scope of the invention. FIGURE 7 is a cell map with each cell divided into six sectors and six sub-frames according to a third embodiment of the invention. The allocation scheme shown in FIGURE 7 is similar to the allocation scheme described above with reference to FIGURE 6. In FIGURE 7, however, the time intervals are now grouped in sub-boxes 1 through 6 and the sectors are marked as 1 to 6 in the counterclockwise direction. The marking patterns for the adjacent cells differ by a rotation of 120 degrees. This rotation creates a cell pattern which can be repeated throughout the system. It is important to note that adjacent sectors use different subframes. Under this embodiment, sector i can program the transmission of packets in sub-frame i for i = 1 to 6. This allocation scheme is very similar to the allocation scheme discussed in the first embodiment of the invention with reference to FIGURE 5. Using the allocation scheme discussed with reference to FIGURE 7, it can be seen that if all sectors have a traffic load of less than one sixth of the total capacity of the channel, all the packets are transmitted in different subframes of time, without causing in this way interference with the same cell. Similarly, due to the 120 degree rotation of the tag patterns between the adjacent cells, the adjacent sectors of the adjacent cells also transmit in different subframes of time, thereby avoiding the main sources of interference from the adjacent cells. Consequently, the same frequency can be used in each sector of each cell. This allocation scheme represents a very conservative method since each sector can use only one sixth of the total bandwidth. This method may be appropriate for a radio environment where concurrent packet transmission within the same cell can cause severe interference, or under low traffic conditions. To improve this conservative allocation scheme, a tiered resource allocation protocol (SRA) was introduced to allow a communication site within a cell to have dynamic access to the bandwidth according to its current needs. FIGURE 8 is a diagram illustrating an SRA protocol according to a fourth embodiment of the invention. This SRA protocol is illustrated here using the allocation scheme discussed with reference to FIGURE 7. The SRA protocol maximizes concurrent packet transmissions and minimizes packet collisions at the same time using the spirit of the protocol concept from left to right . As with the modality discussed with reference to FIGURE 6, a programmer creates an original transmission program and a transmission program in excess. The excess transmission program is generated according to the SRA protocol. According to the original transmission program for this modality, the communication sites within each sector are for programming transmissions in each subframe originally assigned to the sector on the left side. In a program of transmission of excess information, the excess of information for a sector, referred to as an initial sector, is programmed for the transmission of the subframes originally assigned to other sectors within the same cell. When the subframes originally assigned to other sectors within the same cells are used to transmit the excess information, those sub-frames are known as sub-boxes of information excess. The programmer selects the subframes of excess information according to a special order. The special order takes advantage of the directional antennas used within the system to minimize the amount of interference that arises from concurrent packet transmissions. Concurrent packet transmissions refer to the use of a single time interval to transmit information from communication sites located in more than one sectors. The SRA protocol generates the special order by ordering the sub-tables of excess information from those sub-boxes originally assigned to sectors that produce less interference for the communication site that generates the excess information (MIN interference), to those sub-boxes originally assigned to sectors which produce the greatest amount of interference (MAX interference). Thus, if the interference due to concurrent packet transmission in the same cell can be tolerated, one sector should use the first subframe of the opposite sector in the same cell after using all the intervals in the initial subframe, doing so both better use of the directional antennas of the base station. After this, the time intervals in the subsectors for the following sectors are used to the opposite sector. To avoid interference due to imperfect antenna patterns from neighboring sectors, .Use sub-frames for sectors adjacent to the initial sector as a last resort. As shown in FIGURE 8, for example, the special order for sector 1 is sub-section 1 (a), sub-section 4 (b), sub-section 5 (c), sub-section 3 (d), sub-section 2 (e) and subchapter 6 (f). In this way, the programmer first programs information for transmission by a communication site in a sector marked as 1 in the time intervals of sub-panel 1 (denoted by a). If the sector has more traffic to send, use sub-box 4, sub-box 5 and so on until sub-box 6. As also shown in FIGURE 8, the order of allocation for the next sector is "staggered" by a rotation to the right in a sub-frame based on the order for the previous sector. In this way, for sector 2, the sequential order for the program of excess information is in sub-boxes 5 (Jb), 6 (c), 4 (d), 3 (e) and 1 (f). Consequently, this method is known as a "stepped" resource allocation method. In addition to the program of excess information that indicates the order of the sub-tables of excess information to be used, the program of excess information also indicates which side of the transmission of the excess information is going to be programmed in the sub-tables of excess of information. information. To achieve this, the programmer uses the spirit of the protocol from left to right. More specifically, the programmer alternates the programming of the transmission of packets for each sub-frame of each of the left or right subframes starting with the initial sub-frame and following with the other sub-frame according to the special order. By. For example, assume that sub-frame 1 is the initial sub-frame of sector 1. The. Sector 1 information is programmed to transmit information in sub-box 1 (a) on the left side. Following the special order for the information excess program for sector 1, the excess information is programmed to be transmitted in sub-box 4 (b) on the right-hand side, followed by sub-box 5 (c) on the left-hand side, the sub-table 3 (d) on the right side, sub-frame 2 (e) on the left side and finally sub-frame 6 (f) on the right side. The purpose of alternating sides is to avoid additional collisions due to concurrent packet transmission, thereby reducing interference and improving system performance. This is especially true in a case where there is uniform traffic entry between the sectors. To better illustrate this concept, consider sub-frame 1 shown in FIGURE 8. According to the SRA protocol, sector 4 uses sub-frame 1 as the second sub-frame (denoted by b) for transmission. To avoid concurrent transmission with sector 1, which starts on the left side of sub-box 1, sub-frame 4 programs the transmission of packets on the right side. In many cases, sector 4 will not have enough packets to send in all the intervals of subframe 1, thus avoiding concurrent transmission with sector 1 as much as possible. The fact that sector 3 needs to transmit in subframe 1 (c) on the order of the SRA implies that sector 1 will have a similar traffic load under uniform traffic conditions. Thus, sector 1 is likely to transmit at all intervals in sub-panel 1. Consequently, the programming direction for sector 3 (left or right) is unlikely to help avoid transmission interference sector 1. By way of contrast, it is likely that sector 4 may not need to transmit at all intervals in sub-panel 1 (which is the second sub-section of sector 4). For the same reasoning applied for the opposite programming directions for sector 1 and 4, since sector 4 program on the right side, sector 3 should start transmission on the left side of sub-panel 1 to avoid possible interference between sectors 3 and 4. The same reasoning applies to the programming directions of other sectors and other subframes of time. To avoid interference, it can be observed from FIGURE 8 that if all the sectors have a traffic load of less than one sixth of the total capacity of the channel, all the packages of the different sectors are transmitted in different subframes of time, without causing interference of this mode within the same cell. Of course, packets are transmitted simultaneously when the traffic load is increased, thereby increasing the level of interference. However, the SRA protocol takes advantage of the characteristics of the directional antennas to allow multiple transmission of concurrent packets while maximizing the SIR.

For a given radio environment and antenna characteristics, network operators can choose a parameter to control (limit) the number of concurrent transmissions without programming transmissions beyond the first few subframes. For example, if the antennas of the base station or the terminal station of the same cell can be sent to the three most simultaneous packets, only the time intervals in sub-boxes a, b and c would be used for the transmission by each antenna. In addition to managing intracell interference, the SRA protocol helps avoid interference from larger sources in neighboring cells. This is particularly true when the traffic load is from low to moderate. To better illustrate this, consider the downlink for sector 1 in the middle cell of FIGURE 7. Sector 2 in the lower cell and sector 3 in the upper cell have the largest sources of interference. Examining the allocation order for sectors 1, 2 and 3 according to the SRA protocol in FIGURE 8, it can be seen that those sectors will not transmit simultaneously, thus not interfering with each other as long as they have a traffic load of less than one third of the total capacity of the channel, that is to say, that they only use the sub-tables a and b for the transmission. Similarly, the uplink for sector 1 in the middle cell of FIGURE 7 will not transmit simultaneously with sectors 2 and 5 of the lower cell, which now becomes the main source of interference. Due to the symmetry of the allocation order and the cell diagram, the SRA protocol, as well as the other embodiments of the invention, avoids the greater interference of each sector in each cell. The SRA protocol varies depending on the traffic load and a control parameter, with the number of concurrent packet transmissions in each cell fluctuating from 1 to 6. The control parameter can be chosen depending on the SIR and other requirements. As with the above embodiments of the invention, the SRA protocol can work with any number of sectors or cells. FIGURE 9 is a graph of normalized performance vs. aggregate charge normalized according to the fourth embodiment of the invention. An approximate analytical model has been developed to study the performance characteristics of the SRA protocol. The model considers a fixed number of terminals (for example, houses) randomly placed across each sector, finite FTB ratios for the base station and antennas of the terminal station, radio path loss and normal logarithmic dimming effects.

FIGURE 9 presents a sample of the numerical results for this analytical model. In this model, each subframe has two time slots, each sector has 20 terminals, the standard deviation of the normal logarithmic dimming is 4 decibels (dB) and the exponent of the path loss is 4. FIGURE 9 presents the performance of the downlink of the SRA protocol for a set of typical FTB relationships of the antennas of the base station and the terminal station, denoted by B and T, respectively as in the figure. The performance depends on the detection threshold SIR (Th). Using modulation and direct compensation schemes, for example, Quadrature Phase Deviation Manipulation (QPSK) and Decision Feedback Compensators (DFE), the threshold typically falls somewhat within 10 to 15 dB. As shown in FIGURE 9, the maximum performance in each sector for the SRA protocol with these parameters ranges from 30% to 75%. That is, while reusing the same frequency to support high user data rates in each sector of each cell, this embodiment of the invention can achieve a throughput of 30% excess. This percentage of performance translates into a very large network capacity. This is because the SRA protocol is capable of selectively enabling the transmission of concurrent packets to increase throughput while avoiding a greater interference to produce a successful reception. Although several modalities are specifically illustrated and described here,, it should be appreciated that the modifications and variations of the present invention are covered by the foregoing teachings and within the point of view of the appended claims without departing from the intended spirit and scope of the invention. For example, although a TDMA system was used to illustrate the different embodiments of the invention, it can be appreciated that any time-based system falls within the scope of the invention. Similarly, although several embodiments of the invention refer to fixed terminal stations, it can be seen that mobile terminal stations fall within the scope of the invention. Another example includes the number of sectors and cells discussed in the different modalities. It can be appreciated that any sector number of those cells falls within the scope of the invention.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (34)

CLAIMS, Having described the invention as above, the content of the following claims is claimed as property.

1. A method for programming transmissions between a plurality of communication sites within a communication system, the communication system has a service area divided into a plurality of sectors, with each sector assigned to a subframe of time in a pattern, wherein the adjacent sectors use different subframes, characterized in that it comprises the steps of: programming the packet communications for the communication sites located within each sector, where each communication site is programmed to communicate the packets in at least one subframe of time for avoid interference from other sectors; and communicate the packages according to the schedule.

2. The method according to claim 1, characterized in that the programming step creates a transmission program of excess information.

3. The method according to claim 2, characterized in that the excess information transmission program indicates when the excess information for an initial subframe should be transmitted to other subframes.

4. The method of compliance with the claim 3, characterized in that the other frames are selected according to a special order.

5. The method of compliance with the claim 4, characterized in that the special order is created by ordering all interference sub-frames MIN to MAX interference.

6. The method of compliance with the claim 5, characterized in that the special order is created using a stepped resource allocation protocol.

7. The method of compliance with the claim 6, characterized in that each sub-frame has a left side and a right side, and the programming step is programmed when each programming site will transmit information of each sub-frame of each left and right side of the sub-frames.

The method according to claim 7, characterized in that the programming step alternates between the programming of transmissions for each sub-frame of each left side and right side of the sub-frames starting with the initial sub-frame and following with the other sub-frames according to the sub-frame. special order.

9. The method according to claim 8, characterized in that the service area has a plurality of cells, and each cell has six sectors.

The method according to claim 9, characterized in that the system has six sub-frames, with each sector within a cell using a different sub-frame.

11. The method according to the claim 10, characterized in that the pattern is created by rotating each cell 120 degrees.

12. The method in accordance with the claim 11, characterized in that the initial sub-frame for sector one is sub-frame one, and the special order comprises sub-frames four, five, three, two and six.

13. The method according to the claim 12, characterized in that when the initial sub-frame is sub-frames two to six, the stepped resource allocation protocol stages the special order a sub-frame, respectively.

14. The method according to the claim 13, characterized in that each subframe has a left side and a right side, and the programming step creates an original transmission program by programming when each communication site must transmit information from the left side and the right side of the subframe.

15. The method according to claim 14, characterized in that the programming step programs the excess information in a first of the other sub-frames of an opposite direction of which the first of the other sub-frames was originally programmed to transmit in the transmission program original.

16. The method according to claim 1, characterized in that the system has a first and second subframe, and each pair of sectors within a cell has a first and second sector, wherein the communication sites within the first sector transmit packets in the first subframe, and the communication sites within the second sector they transmit packets in the second sub-frame.

17. A method for reusing a common frequency in each sector of a communication system, characterized in that it comprises the steps of: identifying the main sources of interference for the communication sites located within each sector; and program packet transmissions in all sectors to avoid interference.

18. The method according to claim 17, characterized in that the programming step schedules packet transmissions to maximize the transmissions of concurrent packets within a cell.

19. A communication system having a plurality of communication sites, the system has a service area divided into a plurality of sectors with a subframe of time allocated to each sector in a pattern where the adjacent sectors use a different sub-frame, characterized in that comprising: a plurality of communication units operatively associated with the service area to communicate between the communication sites using at least one subframe of time; a programmer to program information to communicate in each sub-frame.

20. The system according to claim 19, characterized in that the programmer creates a program for transmission of excess information.

The system according to claim 20, characterized in that the excess information transmission program indicates when the excess information for an initial subframe in other subframes should be transmitted.

22. The system according to claim 21, characterized in that the other sub-frames are selected according to a special order.

23. The system according to claim 22, characterized in that the special order is created by ordering all the subframes of the interference MIN to the interference MAX.

24. The system according to claim 23, characterized in that the special order is created using a stepped resource allocation protocol.

25. The system according to claim 24, characterized in that each sub-frame has a left side and a right side, and the programmer programs when each communication site must transmit information to each sub-frame of each of the left and right side of the sub-frames .

26. The system according to claim 25, characterized in that the programmer alternates between the programming of transmissions for each sub-frame of each left side and right side of the sub-frames starting with the initial sub-frame and following with the other sub-frames according to the special order .

27. The system according to claim 26, characterized in that the service area has a plurality of cells, and each cell has six sectors.

28. The system according to claim 27, characterized in that the system has six sub-frames, with each sector within a cell using a different sub-frame.

29. The system according to claim 28, characterized in that the pattern is created by rotating each cell 120 degrees.

30. The system according to claim 29, characterized in that the initial sub-frame for sector one is sub-frame one, and the special order comprises sub-frames four, five, three, two and six.

The system according to claim 30, characterized in that when the initial sub-frame is sub-frames two to six, the stepped resource allocation protocol stages the special order a sub-frame, respectively.

32. The system according to claim 21, characterized in that each subframe has a left side and a right side, and the programming step creates an original transmission program by programming when each communication site must transmit information from the left side and the side. subframe right.

33. The system according to claim 32, characterized in that the programming step programs the excess of information in a first of the other sub-frames of an opposite direction to which the first of the other sub-frames was originally programmed to transmit in the program of original transmission.

34. The system according to claim 19, characterized in that the system has a first and second subframe, and each pair 'of sectors within a cell has a first and second sector, where the communication sites within the first sector transmit packages in the first sub-frame, and the communication sites within the second sector transmit packets in the second sub-frame.