Telecommunications – Receiver or analog modulated signal frequency converter – With particular receiver circuit
Reexamination Certificate
2001-10-11
2004-09-28
Tran, Cong Van (Department: 2683)
Telecommunications
Receiver or analog modulated signal frequency converter
With particular receiver circuit
C455S574000, C455S127100, C375S222000, C375S361000
Reexamination Certificate
active
06799030
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to wireless radio frequency modems and, more specifically, to a method and apparatus for extending battery life in an RF wireless modem by automatically commanding the RF modem into a low power, auto-sleep-no-coverage mode when coverage is not available.
BACKGROUND OF THE INVENTION
Current wireless radio frequency (“RF”) modems that cooperatively operate with a host computing device (“host computer”) typically include: (1) a radio portion, also called an RF front end or an RF head; (2) a modulator/demodulator portion, also called a baseband processing unit or baseband chip; (3) a central processing unit (“CPU”) or processor; (4) a memory; and (5) an interface. These modems typically operate using software code to communicate between a user and a base station. The above modem components collectively operate during a wireless communications process to receive an electromagnetic RF signal in a receive mode, wherein the RF signal contains information to be extracted from the received RF signal, and in a transmit mode, wherein the components work collectively to transmit an electromagnetic RF signal, and the RF signal contains the information to be transmitted. Moreover, during the receive and transmit modes, the modem components collectively operate to perform three principal modem functions: RF conversion, baseband processing and protocol stack control.
Typically during RF conversion, the RF head receives the RF signal during the receive mode and converts that RF signal into a modulated baseband analog signal and, during the transmit mode, the RF head converts a modulated baseband analog signal into an RF signal for transmission. During baseband processing, the baseband processing unit in the receive mode demodulates the modulated baseband analog signal by extracting a plurality of data bits that correspond to the information being received. In the transmit mode, the baseband processing unit generates the modulated baseband analog signal for processing by the RF head.
As part of the above wireless communications process, data bits being transmitted are wrapped with protocol bits of data to facilitate transmission, routing, and receiving of the data bits. Likewise, this protocol data must be removed to accurately reproduce, in the receiving RF modem, the data that was sent. The adding or stripping of the protocol bits, also called protocol stack control, is generally performed by the processor in the RF modem under the control of a protocol stack software program stored in the RF modem's memory. Finally, the interface feeds the data bits from the host computer to the RF modem for processing and transmission, and feeds to the host computer the reproduced data bits that were extracted from the received RF signal.
The host computer may typically be a battery powered laptop or palmtop computer, or a Personnel Digital Assistant (PDA), such as a Jornada 545 from Hewlett Packard Co., an IPAQ computer from Compaq Corporation, a Palm III or Palm V from Palm Corp. or a Visor from Handspring Corp. The host computer may also be other types of battery powered devices such as a point of sale terminal, a wireless meter reader, a wireless sensor transmitter or some other computing system. Typical interfaces between the wireless RF modem and the host computer are RS-232, USB, Parallel Port, IrDa, PCMCIA, Flash, Compact Flash, or a low voltage serial interface. However, other interfaces are also used, including a variety of other standard or proprietary interfaces.
Moreover, there are many wireless RF standards that must be considered in the design of any wireless RF modem. Some examples include: circuit switched commercial telecommunications standards including AMPS, CDMA (IS95A & B), and GSM; packet switched standards including CDPD, 1XRTT, GPRS, EDGE, W-CDMA and UMTS; and proprietary wide area wireless networks such as Metricom, Re-Flex, FLEX, Mobitex, and ARDIS.
Current technologies are primarily circuit-switched, meaning a continuous circuit transmission allows the network to route continuous data to a single location. Circuit-switched data requires a dedicated radio channel even when no data is being sent. Packet-switched data does not work the same way as circuit-switched data. With packet-switched data, the modem can send bursts and receive bursts of data. Each burst contains a sequence identification number allowing the regeneration of the blocks of data once all data is sent. A radio channel is occupied only for the duration of the data transmission instead of being dedicated to one user continuously.
A brief overview of some of the above standards is as follows. However, details of many of these standards are available through industry organizations. CDPD (Cellular Digital Packet Data) is a packet-data wireless technology developed by AT&T Wireless Services and other cellular carriers based on Internet Protocol (IP) networking. The CDPD wireless communication system exists to allow mobile users access to the Internet via a wireless link. The specification for this system is entitled “A Cellular Digital Packet Data System Specification” (the “CDPD Specification”) Release 1.1 dated Jan. 19, 1995 and is available from Wireless Data Forum, Suite 800, 1250 Connecticut Ave. N.W., Washington, D.C. 20036. CDPD is deployed as an overlay to analog cellular networks. It enables analog networks such as AMPS (Advanced Mobile Phone Service) to carry packetized data alongside voice. It is primarily used to transmit brief messages, read e-mail, and perform some web browsing for, e.g., wireless enabled Personal Digital Assistants and RF wireless modem equipped laptops. CDPD uses either idle voice channels or dedicated data channels depending on network configuration. However, since the modem never makes an actual “phone call,” the channel becomes immediately available for other data users after the transmission. At the switching center, packet services interconnect with the Internet or directly with corporate intranets using traditional networking methods such as frame relay. Service, available in most major cities in the US and Canada, is provided by major cellular companies.
GPRS is another kind of packet-switched data technology that is being developed for GSM networks. 1XRTT is a packet-switched data technology that uses CDMA techniques. Ricochet is a packet-switched data network operated by Metricom in the unlicensed ISM 902 MHz to 928 MHz band. EDGE, 3G, W-CDMA, and UMTS plus others are all planned to use packet data.
In the battery-operated host computing devices described above, e.g., a mobile unit, it is important to conserve power as much as possible. Therefore, in many of the above wireless air standards, and in CDPD in particular, there is an in-coverage sleep mode (or “state”) detailed in the specifications. The RF wireless modem in the mobile unit coordinates a sleep-mode timer value with a base station controller and then issues a command to the control circuitry within the modem to direct the modem into a sleep mode with the parameters set by the negotiation. This in-coverage sleep mode is very efficient and effective. Unfortunately, if the mobile unit moves out of the coverage area while it is in a sleep mode then a lot of time and power is spent by the modem in searching and trying to re-establish communications with a base station controller. The battery power consumed while performing this search greatly reduces the mobile unit's standby time, particularly when compared to that enjoyed when the unit is within its service area where a low power mode can be used.
For CDPD for example, most of the operation of the RF wireless modem is defined in the CDPD Specification in two relevant sections. The first section, Section 6.8 in pub. 403 at pp. 58 through 62, describes a sleep mode procedure for in-coverage usage. The in-coverage sleep mode is a coordinated low power mode available and requested from the current CDPD base stations. This in-coverage mode is coordinated in that the registered modem device and the base statio
Barber Douglas
Meyer Kevin
Coudert Brothers LLP
Novatel Wireless Inc.
Tran Cong Van
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