U.S. patent application number 10/338434 was filed with the patent office on 2003-07-31 for interface between standard terminal equipment unit and high speed wireless link.
Invention is credited to Bender, Paul E., Grob, Matthew S., Karmi, Gadi, Kimball, Robert H..
Application Number | 20030145119 10/338434 |
Document ID | / |
Family ID | 22566485 |
Filed Date | 2003-07-31 |
United States Patent
Application |
20030145119 |
Kind Code |
A1 |
Bender, Paul E. ; et
al. |
July 31, 2003 |
Interface between standard terminal equipment unit and high speed
wireless link
Abstract
A system provides wireless data service. The system includes a
wireless modem configured to be coupled to a terminal equipment
unit over a wireline broadcast medium. A network unit is coupled to
the wireless modem over a wireless link connection. A network
remote server is coupled to the network unit. The network remote
server provides IP address information in response to terminal
equipment unit address request messages for terminal equipment
units coupled to the network unit. In addition, a local server is
coupled to the wireless modem. The local server provides IP address
information in response to terminal equipment unit address request
messages from terminal equipment units coupled to the wireline
broadcast medium.
Inventors: |
Bender, Paul E.; (San Diego,
CA) ; Grob, Matthew S.; (La Jolla, CA) ;
Kimball, Robert H.; (San Diego, CA) ; Karmi,
Gadi; (San Diego, CA) |
Correspondence
Address: |
Qualcomm Incorporated
Patents Department
5775 Morehouse Drive
San Diego
CA
92121-1714
US
|
Family ID: |
22566485 |
Appl. No.: |
10/338434 |
Filed: |
January 7, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10338434 |
Jan 7, 2003 |
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09158046 |
Sep 22, 1998 |
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6535918 |
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Current U.S.
Class: |
709/249 |
Current CPC
Class: |
H04L 61/50 20220501;
H04L 61/00 20130101; H04W 8/205 20130101; H04L 9/40 20220501 |
Class at
Publication: |
709/249 |
International
Class: |
G06F 015/16 |
Claims
What is claimed is:
1. An apparatus comprising: a wireless modem, configured to be
coupled to a wireline broadcast medium and a wireless link
connection, to send a message requesting an Internet Protocol (IP)
address over the wireless link connection to a network remote
server, to receive the IP address over the wireless link
connection, and to pass an address request message; and a network
local server, coupled to the wireless modem, configured to store
the received IP address, and to provide the stored IP address in
response to the address request message passed from the wireless
modem.
2. A method of assigning Internet Protocol (IP) addresses, the
method comprising the steps of: a) sending an address request
message to a network remote server over a wireless link using a
point to point protocol; b) receiving an assignable IP address from
the network remote server in response to the address request
message over the wireless link; c) receiving a request for an IP
address from a terminal equipment unit over a wireline broadcast
medium; and d) locally generating a responsive IP address
assignment message comprising the assignable IP address for
transmission to the terminal equipment unit over the wireline
broadcast medium.
3. A method of assigning Internet Protocol (IP) addresses in a
wireless communication system comprising the steps of: receiving a
request for an IP address from a standard terminal equipment unit
over a wireline broadcast medium; generating a responsive IP
address assignment message at a local server associated with the
wireline broadcast medium, the responsive IP address assignment
message comprising an assignable IP address; receiving an
encapsulated IP message over the wireline broadcast medium from the
standard terminal equipment unit; extracting the encapsulated IP
message; and forwarding a corresponding extracted IP message over a
wireless link to a network unit.
4. A wireless modem comprising: means for sending an address
request message to a network remote server over a wireless link
using a point to point protocol; means for receiving, over the
wireless link, an assignable Internet Protocol (IP) address from
the network remote server in response to the address request
message; means for receiving a request for an IP address from a
terminal equipment unit over a wireline broadcast medium; and means
for generating a responsive IP address for transmission to the
terminal equipment unit over the wireline broadcast medium.
5. Apparatus for assigning Internet Protocol (IP) addresses, the
apparatus comprising: a. a local server configured to: i. send an
address request message to a remote network server over a wireless
link; and ii. receive an assignable IP address from the remote
network server in response to the address request message; and b. a
processor configured to: i. receive a request for an IP address
from a terminal equipment unit over a wireline broadcast medium;
and ii. generate a responsive IP address assignment message
comprising the assignable IP address for transmission to the
terminal equipment unit over the wireline broadcast medium.
6. A system comprising: a network infrastructure configured to
assign a plurality of IP addresses; a wireless link connection
coupled with the network infrastructure; a wireline broadcast
medium; a wireless modem, coupled with the wireless link connection
and the wireline broadcast medium; and a local server, coupled with
the wireless modem; wherein, the wireless modem sends, over the
wireless link connection to the network infrastructure, a request
for the plurality of IP addresses, the network remote server sends,
over the wireless link connection to the wireless modem, the
plurality of IP addresses; the local server stores the plurality of
IP addresses.
Description
CLAIM OF PRIORITY UNDER 35 U.S.C. .sctn.120
[0001] The present Application for Patent is a Continuation in
Part/Continuation and claims priority to patent application Ser.
No. 09/158,046 entitled "INTERFACE BETWEEN STANDARD TERMINAL
EQUIPMENT UNIT AND HIGH SPEED WIRELESS LINK" filed Sep. 22, 1998,
now allowed, and assigned to the assignee hereof and hereby
expressly incorporated by reference herein.
BACKGROUND
[0002] I. Field of the Invention
[0003] The invention relates to wireless communication systems.
More particularly, the invention relates to techniques of
interfacing data terminal equipment units to wireless data
networks.
[0004] II. Description of the Related Art
[0005] Large networks for interconnecting computers have been
readily available and yet constantly evolving since the mid-1980's.
The largest and most commonly known digital data network is the
Internet. In general, networks provide for the communication of
digital data between two data terminals. In addition to the
Internet, many organizations have private networks to which access
is limited to a select number of users. For example, a corporation
may have an internal data network which interconnects its
computers, servers, dumb terminals, printers, inventories and test
equipment using a wired Ethernet topology.
[0006] Typical networks operate based on the transfer of groups of
bits, called frames. Thus, an entire file of data, such as an
e-mail message, is segmented into a series of frames for
transmission over the network. The actual data represented in each
frame is attached to a series of headers associated with a set of
protocol layers. Each protocol layer is devoted to handling one or
more of the issues involved with the transportation of data between
terminals.
[0007] Most digital networks are comprised of many nodes. On its
journey through the network, a frame may pass through a series of
network nodes. The nodes may be repeaters, bridges, routers,
switches or gateways depending, generally, on the highest protocol
layer which is examined by the node and whether the node transforms
the data from one transport protocol to another.
[0008] The nodes may be connected using a variety of different
physical media, referred to as links. With the advent of wireless
communication techniques, some data networks now include nodes
which are connected by a wireless medium. Through the use of such a
system, rather than being tethered to a wired connection to a
physical data port, the user may transport his terminal to a remote
location and still have access to the network.
[0009] FIG. 1 is an exemplary embodiment of a terrestrial wireless
communication system 10. FIG. 1 shows three remote units 12, 13,
and 15 and two base stations 14. In reality wireless communication
systems may have many more remote units and base stations. In FIG.
1, the remote unit 12 is shown as a mobile telephone unit installed
in a car. FIG. 1 also shows the fixed location remote unit 15 in a
wireless local loop system and the portable computer remote unit 13
in a standard cellular system. In the most general embodiment, the
remote units may be any type of communication unit. For example,
the remote units may be hand-held personal communication system
(PCS) units, portable data units such as a personal data assistant,
or fixed location data units such as meter reading equipment. FIG.
1 shows a forward link 18 from the base stations 14 to the remote
units 12, 13 and 15 and reverse link 19 from the remote units 12,
13 and 15 to the base stations 14.
[0010] Several commercial systems exist which provide true mobility
to the user for data and voice services. The system illustrated in
FIG. 1 may use code division multiple access (CDMA), time division
multiple access (TDMA), a combination of frequency hopping and TDMA
(such as Global System for Mobile Communication (GSM)) or other
modulation and access techniques. In the past, standards using each
of these communication techniques have been initially developed to
provide voice services. The remote units using existing voice
standards have been adapted to provide data services--for example,
to act as nodes within a digital internetwork.
[0011] However, higher performance wireless data networks may be
developed for data-only applications. Without the need for
constraints imposed by voice operation, a data-only network can be
designed which provides much higher rates than that achievable by
the adaptation of the wireless voice systems.
[0012] FIG. 2 illustrates a prior art system which provides
wireless digital communication for terminal equipment unit 30.
Generally, the terminal equipment unit 30 may be any type of
terminal which produces digital information. For example, the
terminal equipment unit 30 may be a personal notebook computer, a
printer, test equipment, a server, a dumb terminal or a variety of
other equipment. Digital data produced by the terminal equipment
unit 30 is passed to a wireless modem 32 via a standard digital
link. For example, the terminal equipment unit 30 may be connected
to the wireless modem 32 via a bi-directional RS-232 bus. The
wireless modem 32 provides an interface to a wireless link 34 and
network infrastructure 36. When communications are established
between the terminal equipment unit 30 and other equipment
connected to the network infrastructure 36, the wireless modem 32
and the terminal equipment unit 30 exchange digital data over the
RS-232 bus. The RS-232 bus is an industry standard serial link
physical layer over which data formatted in a variety of higher
layer protocols may pass.
[0013] As noted above, with the advent of data-only wireless
networks, the speed at which data may travel across the wireless
link has increased significantly. In fact, today the data rate
which may be achieved over the wireless link exceeds the maximum
data rate which may pass over an RS-232 link. In order to reap the
benefits of increased data speeds over the wireless link, the
wireless modem must exchange data with the terminal equipment unit
at a rate which is similar to the highest data rate available over
the wireless link. Thus, it becomes apparent that the RS-232 link,
as used in prior art configurations, becomes a limiting factor
which prevents the terminal equipment unit 30 from taking advantage
of the increased data rates available on the wireless link 34.
[0014] One important criterion when designing a wireless modem is
that the interface with the terminal equipment unit be in
accordance with an accepted industry standard. Aside from RS-232,
another such industry standard is Ethernet. Ethernet was developed
for wired applications and is not particularly suited for a
wireless environment. For example, Ethernet is a broadcast system.
In other words, all stations on an Ethernet network receive all
messages regardless of whether the station represents the intended
destination. Each station must examine the received frames to
determine if the station is the destination. If the station is the
intended destination, the frame is passed to a higher protocol
layer for appropriate processing at the station. If the current
station is not the proper destination, the station simply discards
the frame.
[0015] Each station in an Ethernet system is assigned a hardware
address. The hardware address is contained on the Ethernet
interface card and is permanent and unique to the Ethernet
interface card hardware. Groups of Ethernet stations which time
multiplex their signaling on a common Ethernet connection are
called a subnet. When a station on an Ethernet subnet sends a
message to a station outside of its Ethernet subnet, it sends it to
a gateway associated with the Ethernet subnet. Each Ethernet frame
begins with a preamble. Following the preamble, the frame comprises
the hardware address of the destination station and the hardware
address of the source station. Within the Ethernet frame, the
source address is always a unicast address meaning that the source
always indicates the address of the terminal equipment unit which
is sending the message. The destination address may be unicast (to
single node), multicast (to group of nodes), or broadcast (to all
nodes on the Ethernet subnet) address.
[0016] Because of the finite availability of spectral resources,
the capacity of the wireless link is a very precious resource.
Broadcasting a single message to a large number of stations
consumes significant resources. For this reason, it is not
practical to operate a wireless link using Ethernet-type broadcast
messaging.
[0017] However, as stated above, it is important to use standard
terminal equipment unit interface mechanisms when introducing a
wireless link into a digital data network. Therefore, a need exists
in the industry to provide an interface between standard terminal
equipment units and a high speed wireless link.
SUMMARY
[0018] A wireless modem is used to connect a wireline broadcast
medium terminal equipment unit, such as an Ethernet unit, to a
network unit over a wireless link. In order to avoid the
transmission of broadcast messages from the network unit over the
wireless link, a local server is incorporated within the wireless
modem. When the terminal equipment unit sends a request for an
address to the network unit, the wireless modem intercepts the
message. The local server assigns an IP address to the terminal
equipment unit and responds to the terminal equipment unit. In this
way, the terminal equipment unit need not be modified in any
way.
[0019] The wireless modem receives packets from the terminal
equipment unit over the wireline broadcast medium from the terminal
equipment unit and forwards it over the wireless link to the
network unit using a conventional wireless protocol. In addition,
the wireless modem routes packets received over the wireless link
addressed to the terminal equipment unit to the wireline broadcast
medium.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The features, objectives, and advantages of the invention
will become more apparent from the detailed description set forth
below when taken in conjunction with the drawings:
[0021] FIG. 1 is an exemplary embodiment of a terrestrial wireless
communication system in which mobile data and voice service is
provided.
[0022] FIG. 2 is a block diagram illustrating a prior art system
which provides wireless digital communication for a terminal
equipment unit.
[0023] FIGS. 3A, 3B and 3C are a block diagram and two
corresponding protocol layer diagrams showing a data system
comprising a wireless link.
[0024] FIG. 4 is a block diagram showing a data system comprising a
wireless link in which a single wireless modem services multiple
terminal equipment units.
DETAILED DESCRIPTION
[0025] FIG. 3A is a block diagram showing a data system comprising
a wireless link 56. A standard terminal equipment unit 40 is
connected to a wireless modem 42 via an Ethernet connection.
Ethernet defines a wired physical layer and a link layer protocol
used to connect two or more terminal equipment units. The physical
layer defines the electrical, mechanical, procedural and functional
specifications for activating, maintaining and deactivating the
physical link between two or more stations on the network. Such
characteristics as voltage levels, timing of voltage level
transitions, physical data rates, maximum transmission distances,
physical connector types, and other similar attributes are defined
by the physical layer specification. The link layer provides
reliable transmission of data across the physical link. In doing
so, the link layer is concerned with the physical addressing,
network topology, error notification, ordered delivery of frames
and flow control.
[0026] As noted above, Ethernet operates using broadcast messages.
In a broadcast system, each station in the network examines each
data frame to determine whether the frame is intended for the
station. Because in a broadcast system each message may be sent to
every station on a network, a broadcast system does not provide an
efficient use of wireless link resources because it may require
transmission of messages to stations to which the messages are not
intended.
[0027] Therefore, the wireless modem 42 in FIG. 3A acts as a
gateway between an Ethernet system connecting the terminal
equipment unit 40 and the wireless modem 42 and a standard Internet
Protocol (IP) suite system connecting the wireless modem 42 and a
network unit 58 over the wireless link 56. The IP suite may be used
to internetwork a diverse range of local area networks (LANs) and
wide area networks (WANs). For example, in the last twenty years,
networks have been implemented which operate according to Ethernet,
Token Ring, X.25, Frame Relay, Integrated Services Digital Network
(ISDN), and Asynchronous Transfer Mode (ATM). The IP suite provides
a means of interconnecting each of these networks with any of the
others.
[0028] Within the wireless modem 42, a set of transceivers 44 and
46 facilitate communication over the Ethernet connection and the
wireless link connection 56 respectively. Typically, the
transceiver 44 comprises a standard Ethernet communication card.
The transceiver 46 typically comprises a wireless link
communication module to perform the radio link protocol and
physical layer functions. A processor 48 controls the operation of
the wireless modem 42. The processor 48 interfaces with the
transceivers 44 and 46 as well as a memory unit 50. The memory 50
may store executable program code as well as other forms of
data.
[0029] FIG. 3B is a diagram illustrating a series of protocol
stacks, each stack illustrating the operation of the corresponding
functional block shown above it in FIG. 3A. The protocol stacks of
FIG. 3B illustrate the operation of the system when data is passing
over the wireless link 56. In general, each of the stacks operates
using at least a portion of the IP suite. The IP suite is the most
widely implemented multi-vendor protocol suite in use today. The IP
layer provides internetwork routing based upon an IP address field
found in each IP frame or datagram as they are commonly called.
Additional information concerning the IP suite can be found in
Request For Comment (RFC) 791 entitled "Internet Protocol: DARPA
Internet Program: Protocol Specification" and dated September 1981.
The RFC series of documents specify Internet standards for the
Internet community and request discussion and suggestion for
improvements.
[0030] IP addresses are globally unique. Typically, IP addresses
are 32 bit numbers assigned by a network information center, such
as a dynamic host configuration protocol (DHCP) unit or a bootstrap
protocol (BootP) unit. Globally unique addresses permit IP networks
anywhere in the world to communicate with each other.
[0031] After the establishment of a connection between the terminal
equipment unit 40 and a far end unit coupled to the network unit
58, a higher level protocol layer within the terminal equipment
unit 40, such as an application layer protocol, creates data which
is passed to an IP layer 70. The IP layer 70 produces IP datagrams
which are passed to an Ethernet layer 72. The Ethernet layer 72
encapsulates the IP datagrams into Ethernet data packets. The IP
address designated within the IP datagram is the IP address of a
far end unit coupled to the network unit 58. Therefore, the
Ethernet layer 72 encapsulates the IP datagram in an Ethernet frame
designating the hardware address of the wireless modem 42 which
acts as an Ethernet gateway. The terminal equipment unit 40
broadcasts the Ethernet message over the Ethernet link and it is
received by the wireless modem 42. Within the wireless modem 42, an
Ethernet layer 74 strips off the Ethernet encapsulation to retrieve
the IP datagrams and passes them to an IP layer 78. The IP layer 78
passes the IP datagrams to a point-to-point protocol (PPP) layer
80. The PPP layer 80 operates according to industry standards and
is generally designed for use in a variety of point-to-point
connections such as serial Internet connections. The PPP layer 80
may be used for link establishment, configuration and testing the
connection of two peer nodes over a bit or byte stream. The PPP
layer 80 provides a method for encapsulating multi-protocol
datagrams. The PPP layer 80 also provides negotiation for
compression and encryption methods for a connection. Additional
information concerning the PPP layer 80 may be found in RFC-1661
entitled "The Point-to-Point Protocol (PPP)" and is well-known by
those skilled in the art. In addition to PPP, any protocol which
frames packets through a byte stream may be used in conjunction
with the invention.
[0032] The PPP layer 80 interfaces with a radio link protocol layer
(RLP) 82. The RLP layer 82 enhances the error performance of the
radio link and makes it equivalent to that of a typical landline
connection. The RLP layer 82 interfaces with a physical layer 84.
The physical layer protocol defines the waveform, modulation,
interleaving and encoding of the wireless link signal. The physical
layer 84 passes frames of data over the wireless link 56. Within
the network unit 58, a corresponding physical layer 86, RLP layer
88, PPP layer 90, and IP layer 92 perform the logical converse of
the operations performed the wireless modem 42 to produce IP
datagrams. The IP datagrams can be transferred directly over an
internetwork. Likewise, when an IP datagram arrives at the network
unit 58 specifying the IP address of the terminal equipment unit
40, the analogous reverse operations are performed.
[0033] Before the terminal equipment unit 40 can transmit or
receive IP datagrams over the wireless link 56, the terminal
equipment unit 40, as well as the wireless modem 42, must be
assigned an IP address so that each may be addressed individually
within the system. In addition, the use of independent IP addresses
allows the terminal equipment unit 40 and the wireless modem 42 to
exchange IP messages intended for one another. In FIG. 3A, the
network unit 58 is associated with a network remote server 60
which, among other functions, monitors for broadcast messages from
wired terminal equipment units connected to the network unit 58
according to a standard network information center protocol. The
process of assigning IP addresses to stations on a network is a
part of network management. Network management refers to the
network's ability to manipulate its own resources from a central
location using the network itself as a communication and
configuration medium. One area of network management is network
initialization. In an IP system, it is advantageous to have the
network determine each station's network settings rather than
having the settings fixed within the station or programmed by the
human user. In this way, changing an IP address numbering scheme,
for example, only requires changes on a few servers rather than
manual IP address changes on each station in the network. Also, by
allocating the assignment of IP addresses to the network remote
server 60, the users themselves need not comprehend the process of
assigning IP addresses.
[0034] In a standard wireline network operating according to the IP
suite, when a terminal equipment unit is first powered on, it
broadcasts a message intended for the network remote server 60. The
broadcast message specifies the terminal equipment unit's permanent
hardware address and the terminal equipment unit's need for an IP
address. Several standard network information center protocols have
been developed such as BootP or DHCP. BootP is a simple method of
assigning IP addresses based on Ethernet addresses. Additional
information concerning BootP may be found in RFC-951 entitled
"Bootstrap Protocol (BOOTP)." DHCP is structured as an extension to
BootP and can communicate additional information to the requesting
unit making it a popular solution to local area network host
initialization. Additional information concerning DHCP may be found
in RFC-2131 entitled "Dynamic Host Configuration Protocol."
[0035] In response to the broadcast request from the terminal
equipment unit, the network remote server 60 broadcasts a reply
message. Commonly, the reply message is broadcast because the
requesting unit does not yet know its IP address and, therefore,
cannot be directly addressed using the IP protocol. The reply
message comprises the hardware address of the requesting unit and
the IP address which is being assigned to that unit. As noted
above, with the introduction of the wireless link 56 to the system
shown in FIG. 3A, it is advantageous to avoid broadcasting messages
in order to conserve the bandwidth and capacity of the wireless
link 56.
[0036] When power is initially applied to the terminal equipment
unit 40 and the wireless modem 42, each of them has a unique
hardware address. The Ethernet system is set up such that the
terminal equipment unit 40 and the wireless modem 42 are stations
on an Ethernet subnet. In addition, the wireless modem 42 is
defined as a gateway between the Ethernet subnet and an external
network.
[0037] One commonly used means to initialize a connection is to use
the IP address negotiation feature built into the PPP layers 80 and
90. However, the PPP layers 80 and 90 are not adapted to handle
multiple IP addresses and, therefore, are not adapted to provide
both the wireless modem 42 and the terminal equipment unit 40 with
a separate IP address. For this reason, a new means of negotiating
an IP address must be incorporated into the system of FIG. 3A which
does not rely on the IP address negotiation feature provided by the
PPP layers 80 and 90 and does not require broadcast messages to be
transmitted over the wireless link 56.
[0038] In one embodiment of the invention, the wireless modem 42 is
preassigned an IP address for its own use and is supplied with an
IP address for assignment to the terminal equipment unit 40. The
assignable addresses are stored within a local server 52. In a
typical embodiment, the local server 52 is integrated into a common
structure and housing with the wireless modem 42. FIG. 3C is a
series of two protocol stack diagrams, each illustrating the
operation of the corresponding functional block shown above it in
FIG. 3A. The protocol stacks of FIG. 3C illustrate the operation of
the system when the terminal equipment unit 40 and the local server
52 are communicating using a BootP application layer. At power on,
the BootP client protocol layer 96 in the terminal equipment unit
40 creates a broadcast message requesting an IP address and
specifying its own hardware address and passes it to the IP layer
70. The IP layer 70 passes the request message to the Ethernet
layer 72. The Ethernet layer 72 encapsulates the IP address request
message into one or more broadcast Ethernet frames and broadcasts
them over the Ethernet connection according to well-known
procedures.
[0039] The Ethernet layer 74 in the wireless modem 42 receives the
broadcast Ethernet frame. The Ethernet layer 74 extracts the IP
address request message from the broadcast Ethernet frame and
passes it to the IP layer 78. Rather than forward the IP address
request message to the remote server 60, the IP layer 78 passes it
to a BootP server application layer 98. The BootP application
server layer 98 in turn passes the request message to an
application 100 within the local server 52 that provides IP
addresses. The local server 52 assigns one of the stored IP
addresses to the terminal equipment unit 40. The application 100
creates a response message which is passed through the reverse
protocol stack operation from the application 100 to the BootP
client protocol layer 96. In this way, wireless link resources are
not used to convey broadcast messages for IP address response
messages to the terminal equipment unit 40. Accordingly, this
function of the remote server 60 has been allocated to the local
server 52 for purposes of the terminal equipment unit 40.
Alternatively, the terminal equipment unit 40 may have a
preassigned IP address at power on.
[0040] The local server 52 may obtain the IP address for the
terminal equipment unit 40 in one of a variety of ways. For
example, in one embodiment, the wireless modem 42 may create and
send a custom IP address request message which requests one or more
IP addresses from the remote server 60. The custom IP address
request message originates from an application rather than the
lower layer protocols and, in this way, avoids modification of such
standard lower layer protocols. Addition of the custom IP address
request message to the library of functions available at the
wireless modem 42 is not burdensome, because the wireless modem 42
is a new entity running custom application layer software. By
modifying the wireless modem 42 to retrieve one or more IP
addresses for the terminal equipment unit 40, and maybe also for
itself, modification of the terminal equipment unit 40 may be
avoided.
[0041] In another embodiment, the local server 52 may store a set
of one or more permanent IP addresses. The permanent IP addresses
may be addresses within a range defined to be unroutable by the
network unit 58. In this scheme, a standard network address
translation (NAT) unit in the remote server 60 translates the
unroutable address to a routable address before passing the
corresponding datagrams over the network.
[0042] The invention is also directly applicable to a system in
which multiple terminal equipment units are connected via an
Ethernet connection. FIG. 4 is a block diagram showing a data
system comprising a wireless link in which a single wireless modem
services multiple terminal equipment units. Each terminal equipment
unit 40A-40N operates according to the protocol stacks shown in
FIGS. 3B and 3C. At power on, each terminal equipment unit 40A-40N
sends an IP address request message. The wireless modem 42
intercepts each message in turn according to the protocol stack of
FIG. 3C and the local server 52 responds with an IP address
response message. Once the terminal equipment units 40A-40N have
been assigned an IP address, each unit may communicate over the
Ethernet network in turn according to the Ethernet protocol. The
wireless modem 42 processes the information according to the
protocol stack shown in FIG. 3B when appropriate. Also, the
wireless modem 42 may receive information over the wireless link 56
and create Ethernet messages for each terminal equipment unit
40A-40N, in turn.
[0043] The invention may be embodied in other forms without
diverging from its defining characteristics. For example, in the
embodiment shown above, an Ethernet connection is used to couple
the wireless modem to the terminal equipment unit. In a general
embodiment, the connection may be any wireline medium which relies
on broadcast messaging. Likewise, other functions besides IP
address assignment may be relegated to the wireless modem in order
to avoid broadcasting messages over a wireless link. In one
embodiment, the wireless modem and the terminal equipment unit are
housed within a common body. For example, the wireless modem may be
installed within a lap top computer.
[0044] The invention may be implemented in a variety of media
including software and hardware. Typical embodiments of the
invention comprise computer software which executes on a standard
microprocessor or an application specific integrated circuit
(ASIC).
[0045] The wireless link connection may operate under one of a
plurality of well-known or later developed operating protocols. For
example, the wireless link may operate using time division multiple
access, code division multiple access or other interface supporting
a point-to-point connection.
[0046] The invention may be embodied in other specific forms
without departing from its spirit or essential characteristics. The
described embodiment is to be considered in all respects only as
illustrative and not restrictive and the scope of the invention is,
therefore, indicated by the appended claims rather than by the
foregoing description. All changes which come within the meaning
and range of equivalency of the claims are to be embraced within
their scope.
* * * * *