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As used in this book, the term "cable modem" refers to a service that delivers high-speed Internet access to businesses and consumers over cable lines. A separate cable modem or router is usually required to use the service.
The principle medium access method employed by Wi-Fi networks. It is a "listen before talk": method of minimizing (but not eliminating) collisions caused by simultaneous transmission by multiple radios. The 802.11 standards state that a collision avoidance method rather than a collision detection method must be used, because the standard employs half duplex radios—radios capable of transmission or reception, but not both simultaneously. Unlike conventional wired Ethernet nodes, a WLAN station cannot detect a collision while transmitting. If a collision occurs, the transmitting station will not receive an ACKnowledge packet from the intended receive station. For this reason, ACK packets have a higher priority than all other network traffic. After completion of a data transmission, the receiving station will begin transmission of the ACK packet before another node can begin transmitting a new data packet. All other stations must wait a longer pseudo-randomized period of time before transmitting. If an ACK packet is not received, the transmitting station will wait for an opportunity to retry transmission.
See Complementary Code Keying (CCK).
See Code Division Multiple Access (CDMA).
See W-CDMA.
A brand name trademarked and reserved for the exclusive use of the CDMA Development Group (CDG) member companies. It is a digital mobile phone standard based on the CDMA principle, which is used in North America, Korea, and Japan. For migration to third generation mobile telephony, cdmaOne networks can be upgraded to the cdma2000 broadband standard. The following frequencies are supported by cdmaOne: Cellular and PCS Bands: 800MHz, 900 MHz, 1700MHz, 1800MHz, 1900 MHz and all IMT-2000 bands (cdma2000).
A name identifying the third generation technology that is an evolutionary outgrowth of cdmaOne. It offers operators deploying a second generation cdmaOne system a seamless migration path that economically supports upgrade to 3G features and services within existing spectrum allocations for both cellular and PCS operators. Regardless of technology, cdma2000 supports the second generation network aspect of all existing operators (cdmaOne, IS-136 TDMA, or GSM). This standard is also known by its ITU name IMT-CDMA Multi-Carrier (1X/3X). Operators in the U.S., Japan, and South Korea have adopted it. Although cdma2000 is similar to W-CDMA, the two technologies are incompatible.
The first phase in the evolution to 3G is cdma2000 1X, (or 1 times 1.25 MHz carrier). This technology improves packet data transmission capabilities and speeds in the network, while boosting voice capacity by nearly two times over today's CDMA capacities. It provides a data transfer speed of up to 144 Kpps. It is known also as 1xRTT.
A cdma2000 High Rate Packet Data Air Interface Specification that represents the second step in the evolution of cdma2000. This technology brings data rates of up to 2 Mbps to the network. The CDMA 1xEV specification was developed by the Third Generation Partnership Project 2 (3GPP2).
The 1xEV-DV (cdma-2000 1x Evolution for Data & Voice) technology evolution provides integrated voice with simultaneous high-speed packet data, video and video conferencing capabilities. 1xEV-DV is backward compatible with IS-95A/B and cdma2000 1X, allowing an operator evolution for their existing cdma2000 systems.
See Cellular Digital Packet Data (CDPD).
The cell is the basic geographic unit of a wireless system. In the Wi-Fi industry the term refers to the area of radio range or coverage in which wireless devices can communicate with an access point. The size of the cell depends upon the speed of the transmission, the type of antenna used, and the physical environment, as well as other factors. In the cellular telephone industry, the term "cell" refers to the basic geographic unit of a cellular system and is the basis for the generic industry term "cellular." Cells can vary in size depending on terrain and capacity demands.
A term used in the cellular communications industry. It refers to individual locations where there is a specific compilation of equipment: a network transmitter, receiver, antenna signaling, and related base station equipment. Not to be confused with "cell", which is the basic geographic unit of a Wi-Fi system.
See also Base Station.
A term used to describe a wireless radio frequency communication service that delivers data packets over existing cellular phone networks that have been upgraded for CDPD. CDPD is capable of transfer speeds of up to 19.2 kbps. The CDPD packets are sent between pauses in the cellular phone conversations.
This term refers to the physical medium or set of properties that distinguishes one communication path from another. As used in this book, the term "channel" refers to an individual communication path that carries signals at a specific frequency. For example, Wi-Fi channels refer to particular frequencies at which radio waves are transmitted. Channel can also refer to a communication path between two computers or devices.
A tiny electronic circuit on a piece of silicon crystal is oft times referred to as a "chip." These chips contain hundreds of thousands of micro-miniature electronic circuit components. Components are packed and interconnected in multiple layers within a single chip. The surface of the chip is overlaid with a grid of metallic contacts used to wire the chip to other electronic devices. And all of this is done in an area less than 2.5 millimeters square. A chip's components can perform control, logic, and memory functions. Chips are found in the printed circuits of, for example, personal computers, televisions, automobiles, and appliances.
A redundant bit pattern for each bit that is transmitted, which increases a network signal's resistance to interference. By using a chipping code, if one or more bits in the pattern are damaged during transmission, the original data can be recovered due to the redundancy of the transmission.
The "client" is a computer or program "served" by another networked computing device in an integrated network which provides a single system image. The "server" can be one or more computers with one or more storage devices.
A digital communications technology commonly used for 2G and 3G services. Originally developed for military use, CDMA is a multiple access technique, which uses code sequences as traffic channels within common radio channels. There are two CDMA common air interface standards: Cellular (824–894 MHz)-TIA/EIA/IS-95A, and PCS (1850–1990 MHz)-ANSI J-STD-008.
A hardware device or software program that converts analog information streams into digital signals, and vice versa; generally used in audio and video communications where compression and other functions may be necessary and provided by the Codec as well. The various codecs available may specify straight voice (PCM) or compressed voice (ADPCM).
A popular memory card that uses flash memory to store data on a very small card format to make data easy to add to a wide variety of computing devices, including digital cameras, audio devices, computers, PDAs, and photo printers. CompactFlash cards are based on the Personal Computer Memory Card International Association (PCMCIA) PC card specifications. The typical CompactFlash card measures 43 x 36 mm and is available with storage capacities ranging up to 1 gigabyte. There are two types of CompactFlash cards: Type I cards are 3.3mm thick, Type II cards are 5.5mm thick.
A set of 64 eight-bit code words used to encode data for 5.5 and 11 Mbps data rates in the 2.4 GHz band of 802.11b wireless networking. The code words have unique mathematical properties that allow them to be correctly distinguished from one another by a receiver even in the presence of substantial noise and multipath interference. The 5.5 Mbps rate uses CCK to encode 4 bits per symbol, while the 11 Mbps rate encodes 8 bits per symbol (actually, to attain 11 Mbps CCK modulation, 6 bits of the 8 are used to select one of 64 symbols of 8-chip length for the symbol and the other 2 bits are used by QPSK to modulate the entire symbol. This results in modulating 8 bits onto each symbol.
A code generated by inputting a bit of data and then giving the commutator (an apparatus for reversing electrical currents) a complete revolution. A convolutional code is produced by convolutional coders—coders that have memory.
By taking a convolutional code and repeating the process for successive input bits you produce convolutionally encoded output, such as found in a PLCP preamble and signal field. A convolutional coder (a coder that has memory) accepts k binary symbols at its input and produces n binary symbols at its output, where the n output are affected by v+k input symbols. Memory is incorporated because v>0. Code rate R=k/n. Typical values: k, n: 1 – 8; v: 2–60; R: 0.25–0.75
See Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA).
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