Multiplex communications – Communication over free space – Combining or distributing information via time channels
Reexamination Certificate
1999-06-08
2002-03-26
Marcelo, Melvin (Department: 2663)
Multiplex communications
Communication over free space
Combining or distributing information via time channels
C370S443000, C370S459000
Reexamination Certificate
active
06363062
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a wireless radio communications method and, in particular, to a packet data communication method between network nodes.
BACKGROUND ART
Broadband wireless networks operating at the multi gigahertz spectrum have the potential of delivering a multitude of services to customers at diverse locations. The high frequency of the spectrum allows the deployment of wireless networks with high capacity using a large amount of bandwidth per network per spatial region. In former times, the radio spectrum was licensed for individual services or uses, such as television bands, amateur radio bands, aviation bands, etc. Within each band, individual users were licensed on a link basis such that all users within a band were licensed. In 1998, the FCC (Federal Communication Commission) departed from this approach and auctioned a large amount of the radio spectrum in the 27 GHz and 31 GHz bands for use in Local Multipoint Distribution Systems (LMDS). Similar spectral bands were opened for use in Canada, Australia, New Zealand and Argentina. In Europe, the radio spectrum between 24.5 and 26.5 GHz was also assigned for multipoint use. Many countries are in the process of opening different bands at the high frequency spectrum between 10 GHz and 40 GHz for use on a territorial basis rather than on a link per link basis. This main difference of approach in licensing the radio spectrum (territorial versus link) enables the network operator to build a network which covers large topographical area and offers connectivity services to those customers in line of sight relation in the region. This is because millimeter wave transmission depends on line of sight between communicating transmitters and receivers.
The new regulatory arrangement after 1988 led to the development of point to multipoint wireless systems. Those systems are based on series of base stations with sectoral transmitters and receivers covering cells split into sectors which include customers whose transceivers are facing towards the base station's sectoral antenna. Those customers receive the information broadcast downstream from the base station and select the information addressed to them. On the upstream side, in the TDMA (time division multiple access) mode, the base station assigns time slots or, in the FDMA (frequency division multiple access) mode, frequency slots to each one of the remote customers' transceivers to allow polling information based on the amount of information needed to be transmitted by those customers.
The data protocols for communication are known as “layers” because each layer is a level of the communications system, having its own rules and sometimes having people whose only concern is with operation of that level. The concept of “layers” is explained in many data communication texts and may be summarized as follows. Starting with hardware, considered as the lowest layer, the equipment for making radio communication possible, is known as the “physical layer”, while the highest level, which is the application run by the consumer, is known as the “application layer”. Immediately above the physical layer is the “link layer” which manages the transmission of data without error. Then follows the “network layer” which performs a routing function to set up connections across a network. Then follows the “transport layer” which provides addresses to the network layer and determines the size of units in which data are transported. Next follows the “session layer” which arranges commands between terminals, such as “start” and “finish”. Just below the application layer and above the session layers is the “presentation layer” which defines the format of the data presented, overcoming differences in the requirements of different terminals. In wireless networks, there is an additional layer, the “medium access control layer”, or MAC layer, which is used within the network topology as a protocol for data communication between transceivers of interconnected nodes on the network. In the hierarchy of layers described above, the MAC layer would be between the physical layer and the link layer, acting as an interface between the two. In the past, the medium access control (MAC) layer for point to multipoint (PMP) cellular systems was relatively simple and has been in use for many wireless systems, both on the ground, in cellular mobile systems and broadband systems, as well as satellite to ground (VSAT) systems.
The advantage of a point to multipoint (PMP) network with a MAC layer is its simplicity. The main disadvantage of PMP system arises because of the broadcast nature of the downstream link and the polling of the upstream link. When the base station transmits in a certain frequency and time slot (TDMA), all the customers in the sector except the one that receives information are blocked from receiving any information. In the upstream direction, only one customer can transmit at a certain time on a certain frequency. Thus, when the number of customers in a sector increases, the average data rate available per customer decreases.
The second deficiency of the PMP system is the need to establish expensive base stations at a high positions with a good line of sight to all customers. This demands up-front investment.
The third disadvantage comes from the cellular nature of the PMP MAC layer. The nodes can only communicate with their base station sectoral transceiver, and thus no repeating or route diversity can take place. If a line of sight does not exist from a base station to subscriber units, a new base station should be constructed so that all customers can be connected.
In U.S. Pat. No. 5,903,566 to G. Flammer, a multi-node mesh topology wireless network is disclosed for transmitting large data files, block by block. The transmission protocol involves checking the validity of requested blocks of code. For invalid blocks, the source node frees its packet transmit buffer and the process ends. For a valid block, the source node send the block to the destination node then frees its packet transmit buffer and the process ends. The communications protocol for transfer of blocks is not specified.
SUMMARY OF THE INVENTION
In cable applications, mesh topology networks are avoided because for “n” nodes, n(n−1)/2 circuits are required to connect all nodes. However, mesh topology networks are ideal for broadband wireless applications especially when packet data are used for data transmissions, such as in IP (Internet protocol) networks. The current invention relates to a new type of space and time switched MAC layer protocol designed to enable efficient data transmission particularly in mesh topology networks, or other type of network topology on a packet basis.
The advantages of a mesh network are as follows: (1) The network allows repeating information between the nodes thus enables reliable connections between customers and a backbone access point (BAP) via other nodes in the area with whom line of site (LOS) communication can be established, thus achieving high coverage of the relevant area. (2) The network is built around the customers. The network bandwidth capacity increases as the number of nodes (customers) joining the network increases, due to the creation of multiple parallel paths for the data flow. (3) Route diversity and load balancing is enabled by the availability of multiple routes from nodes to other nodes.
The difficulty of implementing this system is the need to have an algorithm to control and synchronize the data transmission between the nodes based on their relative location with an available line of sight distance and an available link, as well as possible interference from burst data traffic originating and terminating at other nodes. In the IP type of network, data packets are randomly generated with random origination and destination cells. Thus, optimal traffic coordination should be adjusted on a packet by packet basis. In addition, in contrast to physically connected networks of fiber or copper, a wireless mesh may have a transceiver and directio
Aaronson Itai
Worfolk Patrick A.
Caly Corporation
Marcelo Melvin
Nguyen Phuongchau Ba
Schneck Thomas
LandOfFree
Communications protocol for packet data particularly in mesh... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Communications protocol for packet data particularly in mesh..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Communications protocol for packet data particularly in mesh... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2868646