Multiplex communications – Communication over free space
Reexamination Certificate
1999-01-26
2002-12-31
Vincent, David (Department: 2732)
Multiplex communications
Communication over free space
C370S468000
Reexamination Certificate
active
06501741
ABSTRACT:
The present invention relates to a method as set forth in the preamble of the appended claim 1 for supporting the quality of service of data transmission in wireless communication according to the Internet protocol, a system as set forth in the preamble of the appended claim 8, and a wireless communication device as set forth in the preamble of the appended claim 14.
The International Standardisation Organisation ISO has developed an open system interconnection (OSI) model for describing the distribution of data transmission in different layers. The layers are, listed from top downwards, an application layer, a presentation layer, a session layer, a transport layer, a network layer, a data link layer, and a physical layer. In view of the present specification, the most essential layers are the physical layer, the data link layer and the application layer.
The European Telecommunication Standards Institute ETSI has defined a standard for a wireless local area network (ETS 300 652), HIPERLAN Type 1 (high performance radio local area network) to be applied e.g. in wireless local area networks of short distances, such as local area networks of offices. In a local area network according to this standard, several devices may be connected which communicate on the same data transmission channel using packet data transmission. The standard defines the two lowermost layers of said OSI model: the physical layer and the data link layer.
The Conference of European Post and Telephone Administrations CEPT has defined a standard TR 22-05 where the frequency range from 5.15 GHz to 5.3 GHz is reserved for data transmission according to the HIPERLAN standard. This frequency range is divided into five channels, each of which being allotted a band width of ca. 23.5 MHz.
FIG. 1
a
shows a reduced example of such a local area network according to the HIPERLAN standard. It consists of terminal nodes
101
a,
101
b,
101
c,
101
d,
a switching node
102
and a gateway node
103
. The terminal nodes
101
a
-
101
d
may communicate directly with each other, or they may communicate via the switching node
102
if there is no direct radio communication between the terminal nodes
101
a
-
101
d
due to e.g. too long a distance or obstacles dampening radio signals. Via the switching node
102
, the terminal nodes
101
a
-
101
d
can also communicate with the gateway node
103
which is coupled to e.g. a wireless local area network
104
or the Internet network. Thus, the terminal node
101
a
-
101
d
can be used as an Internet host, if necessary.
FIG. 1
b
shows the structure of a data transfer packet according to the HIPERLAN standard. First, there is a header which is transmitted at a lower bit rate (LBR) than the other blocks and which includes the address information and the length of the packet. This is followed by a synchronisation block for synchronising the receiver to the data blocks of the packet DB(
1
), DB(
2
), . . . , DB(m) containing the actual information to be transmitted. One packet may contain a maximum of 47 data blocks. Each packet can be addressed to either one receiver (unicast packet) or several receivers (multicast packet). As the third packet type the HIPERLAN standard defines an acknowledgement packet (ACK) by which the receiver of the packet informs about the successful receipt of the packet so that the sender will know if there is a need to retransmit the packet. In packets requiring data transmission in real time, it can be defined that the receipt of the packet is not acknowledged, because the information contained in the packet could be outdated if retransmitted. Packets of this kind are, for instance, packets for audio applications. On the other hand, for some real-time applications with higher quality demands, such as video applications, it is possible to define limited packet acknowledgement, whereby the acknowledgement is transmitted for several packets with one message. In packets not requiring real time, it is possible to define the acknowledgement to be sent after the receipt of each packet.
The transmission and receipt take place on the same channel without external synchronisation. The channel is listened to by the receiver of the transmitting node for a certain time, and if no communication is detected on this channel within this time, it is assumed that the channel is free and transmission is started. However, if communication is detected on this channel, the receiver is synchronised with this transmission. After the transmission, a possible acknowledgement message is waited for, and after this, an attempt for obtaining the channel can be started.
However, there may be several nodes waiting for transmission turns, whereby it may occur that several terminal devices try to transmit simultaneously. This can be solved e.g. so that the nodes are allotted different priorities, whereby a node with a lower priority will wait a longer time after the end of a transmission before it starts to transmit, if no communication is detected on the channel within this time.
The term “Internet” is commonly used to describe an information resource from which information can be retrieved from a data processor, such as a personal computer (PC). The data processor communicates via a modem with a telecommunication network. This information resource is distributed world-wide, comprising several storage locations which also communicate with the telecommunication network. The Internet is made operable by defining certain data communication standards and protocols, such as TCP (transfer control protocol), UPD (user datagram protocol), and IP (Internet protocol), which are used for controlling data transmission between numerous parts of the Internet. The TCP and the UDP are involved with preventing and correcting data transmission errors in the data transmitted in the Internet; the IP is involved with data structure and routing. The currently used versions of the Internet protocol are IPv4 and IPv6.
Thanks to the growing popularity of open data systems, the Transmission Control Protocol/Internet Protocol (TCP/IP) communication protocol has become a generally used protocol whereby computers of different sizes and brands can communicate with each other. TCP/IP support is currently available for almost all operating systems. The network layer protocol of TCP/IP, the Internet Protocol IP, is intended to be routed by gateways, i.e. routers. The routing is conducted by means of IP addresses of four bytes and routing tables. Thanks to the Internet protocol, computers using the TCP/IP can transfer messages in the routing network even to the other side of the world.
The Internet, which covers well particularly the industrialised countries, is a huge network of routers using the TCP/IP communication protocol. The largest group of users of the Internet, which was originally in scientific use only, is now firms which buy their services from commercial connection providers. In the Internet, each device has its own individual IP address. In the Internet protocol version IPv4, the IP address consists of 32 bits, i.e. it is a digit of four bytes which is divided in two parts: an organisation-specific network address and a network-specific device address. For facilitating the processing of addresses, a decimal dot notation system has been introduced, in which the addresses are indicated by digits of 8 bits separated by dots (an octet). One octet is a number from 0 to 255. This address mechanism is further divided into three different classes (ABC) which make network and device addresses of different lengths possible.
Further, with the growing popularity of the Internet, the length of the address blocks in the data packets of Internet messages is no longer sufficient in all situations for indicating all the addresses in use. This is one reason for developing the Internet protocol version IPv6. In this protocol version, the length of the address blocks is increased to 128 bits, which means in practice that an individual address can be reserved for all devices that are connected with the Internet network.
FIG.
Ala-Laurila Juha
Mikkonen Jouni
Nokia Mobile Phones Ltd.
Perman & Green LLP
Vincent David
LandOfFree
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