A wireless network generally includes a network architecture and set of protocols to route data between wireless nodes in the network, often using intermediate nodes as relays in multi-hop routing. Mesh networking typically adjusts the routes between nodes to get around broken, blocked, or poorly performing links along the path between the source and destination node. In particular, mesh networks are self-healing: the network can still operate even when a node breaks down or a connection goes bad. As a result, a reliable network can be formed. Many different neighbor discovery and routing algorithms have been used in mesh networks. These algorithms generally do not take into account multiple antennas at each node with multiple frequency bands that a given node may have access to. State-of-the-art information (as of 2005) regarding wireless communications, including neighbor discovery and routing protocols, can be found in the book Wireless Communications by Andrea Goldsmith, which is incorporated by reference. Areas of ongoing research include, for example, implementing multiple input multiple output (MIMO) technologies, providing an outdoor deployment of broadband networks that are compatible with IEEE 802.11 and other wireless standards.
The foregoing examples of the related art are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.
The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools, and methods that are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other improvements.
Deployment of wireless broadband and systems for use in providing wireless broadband is described. The system can be implemented indoors or outside. In a specific implementation, the system takes advantage of 4×4 multiple-input multiple-output (MIMO) technology and techniques. The system can also or instead take advantage of some other (e.g., 8×8 MIMO) technology and techniques. With appropriate configuration, the system enables industry-leading reliability, at least with respect to packet error rate (PER). The system can include a trunk, which can include a root node, optional repeaters, and a main distribution node, the combination which enables wireless MIMO backhaul to a network such as the Internet. In general, any applicable transmission medium from a main distribution node to point of presence (PoP) or head end can be considered a trunk.
Components of the system include wireless devices. Generic modular units can be implemented “in parallel” for wireless backhaul in a wireless network or on their own for distribution. An optional goal of component design can be system in a package (SiP), though a two chip package, one for radio frequency (RF) and one for baseband, is also a design choice. Advantageously, the wireless devices can use 4×4 MIMO technologies to accomplish digital beamforming and other tasks.
The description in this paper describes this technique and examples of systems implementing this technique.
Examples of the claimed subject matter are illustrated in the figures.
In the following description, several specific details are presented to provide a thorough understanding of examples of the claimed subject matter. One skilled in the relevant art will recognize, however, that one or more of the specific details can be eliminated or combined with other components, etc. In other instances, well-known implementations or operations are not shown or described in detail to avoid obscuring aspects of the claimed subject matter.
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The first relay node in the wireless trunk network 106 is the root node, which can be wire connected to the PoP 104. Zero or more relay nodes are wirelessly connected in series from the root node to the last relay node in the wireless trunk network 106, which can be wirelessly connected to the wireless distribution network 108. A point-to-point relay node is described later with reference to
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Thus, the APs 112 can be referred to as stations, if applicable. In alternative embodiments, a station may comply with a different standard than IEEE 802.11, may be referred to as something other than a “station,” and may have different interfaces to a wireless or other medium. An implementation of the wireless distribution network 108 has been referred to as a wireless PON (WPON) for marketing purposes. It may be noted that the acronym PON is not intended to have the technical meaning it is given in the optical arts because a WPON is not really a wireless “passive optical network.”
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An advantage of implementing a matrix mesh network is that APs trying to reach multiple stations, 3 out of 4 streams could get knocked out and the system would still work. Different streams can survive to get to different stations. It has been shown in a proof of concept that MIMO is more reliable outside than SISO, and can survive seasonal changes to the environment, such as the elements and foliage growing into the wireless transmission path. In a successful test, poles were placed at between 120 and 170 feet, with intervening obstacles including a thick exterior wall and big trees blocking. The access point locations were approximately 5 feet above the ground, and were operated in the 5 GHz band. The average UDP data rate was 110-120 Mbps and the wireless link rate was 180-200 Mbps. Existing systems have much lower data rates than the proof of concept had.
The computer 202 interfaces to external systems through the communications interface 210, which may include a radio interface, network interface, or modem. It will be appreciated that the communications interface 210 can be considered to be part of the computer system 200 or a part of the computer 202. The communications interface 210 can include a radio, an analog modem, ISDN modem, cable modem, token ring interface, satellite transmission interface (e.g. “direct PC”), or other interfaces for coupling a computer system to other computer systems.
The processor 208 may be, for example, a conventional microprocessor such as an Intel Pentium microprocessor or Motorola power PC microprocessor. The memory 212 is coupled to the processor 208 by a bus 220. The memory 212 can be Dynamic Random Access Memory (DRAM) and can also include Static RAM (SRAM). The bus 220 couples the processor 208 to the memory 212, also to the non-volatile storage 216, to the display controller 214, and to the I/O controller 218.
The I/O devices 204 can include a keyboard, disk drives, printers, a scanner, and other input and output devices, including a mouse or other pointing device. The display controller 214 may control in the conventional manner a display on the display device 206, which can be, for example, a cathode ray tube (CRT) or liquid crystal display (LCD). The display controller 214 and the I/O controller 218 can be implemented with conventional well known technology.
The non-volatile storage 216 is often a magnetic hard disk, an optical disk, or another form of storage for large amounts of data. Some of this data is often written, by a direct memory access process, into memory 212 during execution of software in the computer 202. In general, an engine implemented in the system 200 can include a dedicated or shared processor and, hardware, firmware, or software modules that are executed by the processor. Depending upon implementation-specific or other considerations, an engine can be centralized or its functionality distributed. An engine can include special purpose hardware, firmware, or software embodied in a computer-readable medium for execution by the processor. As used in this paper, the term “computer-readable storage medium” is intended to include only physical media, such as memory. As used in this paper, a computer-readable medium is intended to include all mediums that are statutory (e.g., in the United States, under 35 U.S.C. 101), and to specifically exclude all mediums that are non-statutory in nature to the extent that the exclusion is necessary for a claim that includes the computer-readable medium to be valid. Known statutory computer-readable mediums include hardware (e.g., registers, random access memory (RAM), non-volatile (NV) storage, to name a few), but may or may not be limited to hardware.
The computer system 200 is one example of many possible computer systems which have different architectures. For example, personal computers based on an Intel microprocessor often have multiple buses, one of which can be an I/O bus for the peripherals and one that directly connects the processor 208 and the memory 212 (often referred to as a memory bus). The buses are connected together through bridge components that perform any necessary translation due to differing bus protocols.
Network computers are another type of computer system that can be used in conjunction with the teachings provided herein. Network computers do not usually include a hard disk or other mass storage, and the executable programs are loaded from a network connection into the memory 212 for execution by the processor 208. A Web TV system, which is known in the art, is also considered to be a computer system, but it may lack some of the features shown in
In addition, the computer system 200 is controlled by operating system software which includes a file management system, such as a disk operating system, which is part of the operating system software. One example of operating system software with its associated file management system software is the family of operating systems known as Windows® from Microsoft Corporation of Redmond, Wash., and their associated file management systems. Another example of operating system software with its associated file management system software is the Linux operating system and its associated file management system. The file management system is typically stored in the non-volatile storage 216 and causes the processor 208 to execute the various acts required by the operating system to input and output data and to store data in memory, including storing files on the non-volatile storage 216.
Some portions of the detailed description may be presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of operations leading to a desired result. The operations are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.
It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.
Systems described in this paper may be implemented on any of many possible hardware, firmware, and software systems. Typically, systems such as those described in this paper are implemented in hardware on a silicon chip. Algorithms described in this paper are implemented in hardware, such as by way of example but not limitation RTL code. However, other implementations may be possible. The specific implementation is not critical to an understanding of the techniques and the claimed subject matter.
The system 300 includes an N×M antenna array 302, a system in package (SiP) 304, a power source 306, and an (optional) solar array 308. As used in this paper, a SiP is a number of integrated circuits enclosed in a single package that performs most of the functions of an electronic system, in this case a MIMO station. SiP dies containing integrated circuits can be stacked vertically on a substrate and connected by wires. Slightly less dense multi-chip modules can also be used, which place dies on the same plane; and three-dimensional integrated circuits having stacked silicon dies with conductors running through the die can be used. One advantage of implementing the system 300 in a wireless MIMO backhaul system is that the same unit can be used for each node of the backhaul network. Where it is desirable to have greater bandwidth, additional units can be deployed. The units can be configured to operate in the same frequency both upstream and downstream or to operate in different frequencies in each direction.
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Although the N×M antenna array 302 is depicted as outside of the SiP 304, the antenna array could be implemented in the SiP 304, as well. The SiP 304 includes an RF front end 312, a GbE switch 314, a digital MIMO processing block 316, and a power input block 318. A current implementation provides 0.3 Gbps per unit.
The MIMO channel 406 is characterized by a matrix H with M rows and N columns, where N is the number of antennas at the node 402, and M is the number of antennas at the wireless relay node 404. The matrix H describes the channel gains between all transmit-receive antenna pairs of the two matrix mesh elements, i.e. the matrix element hi,j in the ith row and jth column of H is the channel gain between the jth transmit antenna and the ith receive antenna. The transmitted signal is a vector X=[x1, . . . xN], where xj is the signal transmitted from the jth antenna of the node 402. The received signal is a vector Y=[y1, . . . yM], where y is the received signal at the ith antenna of the node 404. The received signal at the ith receive antenna is corrupted by noise and possibly interference ni, and the vector N=[n1, . . . , nM] describes the noise and interference associated with all receive antennas. The received signal vector Y is characterized by the matrix multiplication Y=HX+N, i.e.
so that yi is the sum of signals associated with all transmit signals xj, i=1, . . . , N multiplied by the channel gain hi,j the jth transmit antenna to the ith receiver antenna, plus the additive noise ni associated with the ith receiver antenna.
Depending upon whether there are multiple antennas at a station, in a transmit antenna array, and/or multiple antennas in the receive antenna array, the communication link can be referred to as a MIMO link. It should be noted that multiple-input and single-output (MISO), single-input and multiple-output (SIMO), and single-input and single-output (SISO) are special cases of MIMO. MISO is when the receiver has a single antenna. SIMO is when the transmitter has a single antenna. SISO is when neither the transmitter nor the receiver have multiple antennas. The acronym MIMO could be considered to include the special cases, if applicable. The techniques may also be applicable to multi-user MIMO (MU-MIMO), cooperative MIMO (CO-MIMO), MIMO routing, OFDM-MIMO, or other MIMO technologies. The major consideration with respect to multiple antenna use as it relates to the techniques described in this paper is whether there are multiple antennas at the receiver (MIMO or SIMO) or not (SIMO or SISO). When there are multiple antennas at the receiver, there are typically multiple corresponding RF chains and other components.
The MIMO channel 406 between the wireless relay node 404 transmit antennas 414 and a node 412 receive antennas 416 behaves in a similar fashion. It is not necessarily the case that the number of antennas is the same for the nodes 402, 412. The flow of traffic is in opposite directions for upstream and downstream transmissions. In a typical deployment, there may be a difference between upstream and downstream bandwidth, where downstream bandwidth is often greater than upstream bandwidth.
The multiple antennas between nodes can be used to increase data rates by creating multiple independent channels between the nodes (e.g., via spatial multiplexing): the maximum number of such data paths that can be created is the minimum of N and M. Alternatively, transmitted signals can be combined via transmit diversity or beamforming, and/or the received signals can be combined via receive diversity, which increases link robustness. Also, beamsteering can be done to steer an antenna beam in a given direction, which increases range and/or reduces interference. These techniques are not mutually exclusive, and some antennas can be used for spatial multiplexing, others for diversity, and still others for beamsteering or beamforming.
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Advantageously, deployment of a system, such as described, enables deployment of broadband access that is equivalent to wire. This is made possible by the use of MIMO, which is advantageously less expensive to deploy than wire. While SISO may be cheaper than MIMO to implement, it may not currently be capable of providing access that is equivalent to wire. In an implementation, pole-mounted APs are deployed at 200 meter spacing. Such spacing can be assumed to provide coverage to, for example, 24 homes. With such a spacing and 24 homes within range, it is believed that the cost of deployment can be recouped in 3 years at a cost of about $17.99 per home with 100% penetration. This is a fraction of the cost of deploying wire. The APs need power, of course, but residential indoor and outdoor units would have power supplied by the customer, and pole mounted nodes are expected to have power costs of only $100/year. Power can be supplied using solar panels to eliminate the need to connect backhaul APs to a power grid or the equivalent.
For self-configuration of a matrix mesh network backbone, mesh network elements join the network through a process of neighbor discovery and, once one or more neighbors are found, establishing connections with one or more of these neighbors. Advantageously, due to the longer range and/or better robustness associated with multiple antenna channels, a neighbor discovery protocol designed for a matrix mesh element is likely to be able to establish more robust connections and to identify more neighbors than a discovery algorithm for single-antenna nodes. In an outdoor environment, this can be particularly useful to ensure that not only is the bandwidth associated with the service equivalent to wire, but the reliability also approaches or even matches that of wire.
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Systems described herein may be implemented on any of many possible hardware, firmware, and software systems. Typically, systems such as those described herein are implemented in hardware on a silicon chip. Algorithms described herein are implemented in hardware, such as by way of example but not limitation RTL code. However, other implementations may be possible. The specific implementation is not critical to an understanding of the techniques described herein and the claimed subject matter.
As used herein, the term “embodiment” means an embodiment that serves to illustrate by way of example but not limitation.
It will be appreciated to those skilled in the art that the preceding examples and embodiments are exemplary and not limiting to the scope of the present invention. It is intended that all permutations, enhancements, equivalents, and improvements thereto that are apparent to those skilled in the art upon a reading of the specification and a study of the drawings are included within the true spirit and scope of the present invention. It is therefore intended that the following appended claims include all such modifications, permutations and equivalents as fall within the true spirit and scope of the present invention.
The present application claims priority to U.S. Provisional Patent App. No. 61/227,053, filed on Jul. 20, 2009, which is incorporated by reference.
Number | Date | Country | |
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61227053 | Jul 2009 | US |