Unit 7

WiMAX

___________ is a broadband wireless access network that aims to cover an entiremetropolitan area. It would seem that WiMAX is a direct competitor to 3G cellular networks, but ___________ is based on the IEEE 802.16 protocols that are very different from such 3G protocols as UMTS.

IEEE 802.16

___________ specifies a frequency range of 2 GHz up to 66 GHz although, in reality, network operators will only be licensed to operate in a much narrower band. The ___________ standard is capable of covering a range of 50 km with a bit rate of 75 Mbps (Ghazal & Ben-Othman, 2008).

loss of decoder synchronization

for digital video coding, when there is damage to a packet containing variable bit-length data, that error, if unconstrained, will propagate all the way throughout the stream

Wideband CDMA

3G networks have been predominantly using ___________. A wider channel bandwidth is allocated to support bitrates of up to 2 Mbps.

FDMA

Frequency Division Multiple Access One of the modulation techniques used in cellular wireless networks. It divides the frequency range into bands and assigns a band to each subscriber. FDMA was used in 1G cellular networks

2G

Second-generation (2G) wireless networks use digital technology. Besides voice, digital data is increasingly transmitted for applications such as text messaging, streaming audio, and electronic publishing. In North America, the digital cellular networks adopted two competing technologies in 1993: Time Division Multiple Access(TDMA) and Code Division Multiple Access (CDMA). In Europe and Asia, Global System for Mobile communications (GSM) [1], which used TDMA, was introduced in 1992.

synchronization marker

These enable enable decoder resynchronization. For example, the H.263 bitstream has four layers - the Picture layer, GOB layer, Macroblock layer, and Block layer. The Picture Layer starts with a unique 22-bit picture start code (PSC). The longest entropy-coded symbol possible is 13 bits, so the PSC serves as a ________________ as well. The GOB layer is provided for synchronization after a few blocks rather than the entire frame. The group of blocks start code (GBSC) is 17 bits long and also serves as a ________________ .The macroblock and the Block layers do not contain unique start codes, as these are deemed high overhead.

UMTS

_________ QoS Classes: conversational, streaming, interactive, and background according to the time-delay sensitivityof each. Each QoS class consists of a set of parameters, including throughput (maximum and guaranteed kbps), packet size, order of delivery, error ratio, delay, and priority. This makes the QoS more scalable and customizable.

traffic flow

______________ (computer networking) In packet switching networks, _____________, packet flow or network flow is a sequence of packets from a source computer to a destination, which may be another host, a multicast group, or a broadcast domain.

bose-chaudhuri-hocquenghem (BCH) codes

______________ can be encoded and decoded quickly using integer arithmetic, since they use Galois fields. H.261 and H.263 use BCH to allow for 18 parity bits every 493 source bits. Unfortunately, the 18 parity bits will correct at most two errors in the source. Thus, the packets are still vulnerable to burst bit errors or single-packet errors.

QoS profile

A ______________ is supported by the bearer service to allow for end-to-end QoS, based upon a set of four parameters: priority, reliability, delay parameters, and throughput parameters.

spread spectrum

the bandwidth of a signal is spread before transmission - it's secure and robust against intentional interference - applicable to digital and analog signals because both can be modulated and "spread" -

1) block codes, 2) hamming distance

These codes are referred to as (n, k) codes. The two types of ___1___ are linear and cyclic. All error correction codes operate by adding space between valid source strings. The space is measured using a ___2___, defined as the minimum number of bits between any coded strings that need to be changed so as to be identical to a second string.

Bluetooth

Allows electronic devices like cell phones and computers to exchange data over short distances using radio waves Uses Frequency Hopping at the 2.4GHz ISM band Employs a master-slave structure. One master may communicate with up to seven slaves in a piconet; all devices share the master's clock. - Transmission speed can be over 700 kbps with a distance of 10m

TDMA

Creates multiple channels in multiple time slots while allowing them to share the same carrier frequency. Combined with FDMA - the entire allocated spectrum is first divided into multiple carrier frequency channels, each of which is further divided in the time dimension by TDMA

GSM

established by European Conference of Postal and Telecommunications Administrations in 1982 - GSM 900: operates at 900 MHz frequency - GSM 1800: original GSM standard modified to operate at the 1.8GHz frequency range - GSM 1900: In NA, GSM uses frequencies at the range of 1.9GHz

Error Concealment

Despite all the efforts to minimize occurrences of errors and their significance, errors can still be visually annoying. ________________ techniques are thus introduced to approximate the lost data on the decoder side.

sender-receiver feedback

For interactive applications, if a back channel is available to the encoder, a few additional error control techniques are available, classified as _______________. According to the bandwidth available at any moment, the receiver can ask the sender to lower or increase the video bitrate (transmission rate control), which combats packet loss due to congestion. If the stream is scalable, it can also ask for enhancement layers.

Next Generation Networks (NGN)

The _______________ is a body of key architectural changes in telecommunication core and access networks. The general idea behind the _______________ is that one network transports all information and services (voice, data, and all sorts of media such as video) by encapsulating these into IP packets, similar to those used on the Internet. _______________ are commonly built around the Internet Protocol, and therefore the term all IP is also sometimes used to describe the transformation of formerly telephone-centric networks toward _______________ .

direct sequence

The foundation of CDMA is __________ (DS) Multiple CDMA users can make use of the same (and full) bandwidth of the shared wideband channel during the entire period of transmission. Reuse factor K = 1. It has the potential of greatly increasing the maximum number of users as long as the interference from multiple users is manageable.

frequency hopping

The transmitter and receiver change predetermined frequencies at the same time (in a synchronized manner).

IEEE 802.11

Wireless Ethernet standard more commonly known as Wi-Fi. Initial ________ standard uses the Industrial, Scientific and Medical (ISM) 2.4GHz radio band. Faces interferences from both of its own users and many other wireless systems.

1G

_______________ cellular phones used analog technology and Frequency Division Multiple Access (FDMA), in which each user is assigned a separate frequency channel during the communication. Its standard was Advanced Mobile Phone System (AMPS) in North America, Total Access Communication System (TACS) and Nordic Mobile Telephony (NMT) in Europe and Asia. Digital data transmission users needed modems to access the network; the typical data rate was 9,600 bps

Reed Solomon Codes

_________________ codes are a subset of BCH codes and are linear block codes. A Reed-Solomon code is specified as RS(n,k) with s-bit symbols. This means that the encoder takes k data symbols of s bits each and adds parity symbols to make an n symbol codeword. There are n-k parity symbols of s bits each.

OFDM

a frequency-based modulation method where each available frequency will be subdivided into several channels in parallel. Frequency channels will be optimized to achieve higher efficiency.

heterogeneous network

a network connecting computers and other devices with different operating systems and/or protocols. For example, local area networks (LANs) that connect Microsoft Windows and Linux based personal computers with Apple Macintosh computers are ___________________.

frame errors and erasure

a technique that adds redundant data to a bitstream to recover some random bit errors in it. Ideally, the channel-packet error rate (or bit error rate) is estimated, and enough redundancy is added to make the probability of en-or after FEC recovery low