通信工程专业英语结课论文(中英)

Modern mobile communication technology

In

now

highly

the

informationization

society,

the

information

and

the

correspondence

have become

the

modern

society

“the

life”. The

information

exchange

mainly

relies

on

the

computer

correspondence,

but

corresponds

takes

the

transmission

method,

with

the

sensing

technology,

the

computer

technology

fuses

mutually,

has

become

in

the

21st

century

the

international

society and the world economic development powerful engine. In order to of

adapt

the

time

request,

the

new

generation

of

mobile

communication

technology seasonable and lives, the new generation of mobile communication

technology is the people said that third generation's core characteristic is the

wide

band

addressing

turns

on

non-gap

roaming

between

the

rigid

network

and

numerous

different

communications

system's,

gains

the

multimedia

communication

services.

the

mobile

communication

technology

to

have

the

following several aspect important technology:

1. wideband modulation and multiple access technique

The

wireless

high

speed

data

transmission

cannot

only

depend

on

the

frequency

spectrum

constantly

the

expansion,

should

be

higher

than

the

present number magnitude at least in the frequency spectrum efficiency, may

use

three

technologies

in

the

physical

level,

namely

OFDM,

UWB

and

free

time

modulation

code.

OFDM

with

other

encoding

method's

union,

nimbly

OFDM

and

TDMA,

FDMA,

CDMA,

SDMA

combines

the

multiple

access

technique.

In the 1960s the OFDM multi-channel data transmission has succeeded

uses in Kineplex and the Kathryn high frequency military channels. OFDM has

used

in

1.6

Mbit/s

high

bit

rate

digital

subscriber

line

(HDSL),

6

Mbit/s

asymmetrical digital subscriber line (ADSL), 100 Mbit/s really high speed figure

subscriber's

line

(VDSL),

digital

audio

frequency

broadcast

and

digital

video

broadcast

and

so

on.

OFDM

applies

on

5

GHz

provides

54

Mbit/s

wireless

1

local network IEEE 802.11 a and IEEE 802.11g, high performance this region

network

Hiper

LAN/2

and

ETSI- BRAN,

but

also

takes

metropolitan

area

network IEEE 802.16 and the integrated service digit broadcast (ISDB-T) the

standard. Compares with the single load frequency modulation system service

pattern, the OFDM modulation service pattern needs to solve the relatively big

peak

even

power

ratio

(PAPR,

Peak

to

Average

Power

Ratio)

and

to

the

frequency shifting and the phase noise sensitive question.

High

speed

mobile

communication's

another

request

is

under

the

wide

noise bandwidth, must demodulate the signal-to-noise ratio to reduce as far as

possible, thus increases the cover area. May adopt the anti- fading the full start

power

control

and

the

pilot

frequency

auxiliary

fast

track

demodulation

technology, like the frequency range anti-fading's Rake receive and the track

technology, the OFDMA technology which declines from the time domain and

the

frequency

range

resistance

time

and

the

frequency

selectivity,

the

link

auto-adapted technology, the union coding technique.

2. frequency spectrum use factor lift technique

The

fundamental

research

pointed

out:

In

the

independent

Rayleigh

scattering

channel,

the

data

rate

and

the

antenna

several

tenth

linear

relationships,

the

capacity

may

reach

Shannon

90%.

Is

launching

and

the

receiving end may obtain the capacity and the frequency spectrum efficiency

gain by the multi- antenna development channel space. The MIMO technology

mainly

includes

the

spatial

multiplying

and

the

space

diversity

technology,

concurrent or the salvo same information enhances the transmission reliability

on the independent channel.

Receives and dispatches the bilateral space diversity is the high-capacity

wireless

communication

system

uses

one

of

technical.

Bell

Lab

free

time's

opposite angle BLAST (D-BLAST) capacity increase to receive and dispatch

the bilateral smallest antenna number in administrative levels the function. The

cross time domain which and the air zone expansion signal constitutes using

MIMO may also resist the multi-diameter disturbance. V-BLAST system when

2

indoor

24~34

dB,

the

frequency

spectrum

use

factor

is

20~40

bit/s/Hz.

But

launches and the receiving end uses 16 antennas, when 30 dB, the frequency

spectrum use factor increases to 60~70 bit/s/Hz.

The

smart

antenna

automatic

tracking

needs

the

signal

and

the

auto- adapted

free

time

processing

algorithm,

produces

the

dimensional

orientation wave beam using the antenna array, causes the main wave beam

alignment

subscriber

signal

direction

of

arrival

through

the

digital

signal

processing

technology,

the

side

lobe

or

zero

falls

the

alignment

unwanted

signal

direction

of

arrival.

The

auto-adapted

array

antennas

(AAA,

Adaptive

Array

Antennas)

disturbs

the

counter-balance

balancer

(ICE,

Interference

Canceling Equalizer) to be possible to reduce disturbs and cuts the emissive

power.

3. software radio technology

The

software

radio

technology

is

in

the

hardware

platform

through

the

software edition by a terminal implementation different system in many kinds of

communication

services.

It

uses

the

digital

signal

processing

language

description

telecommunication

part,

downloads

the

digital

signal

processing

hardware by the software routine (DSPH, Digital Signal Pocessing Hardware).

By

has

the

general

opening

wireless

structure

(OWA,

Open

Wireless

Architecture),

compatible

many

kinds

of

patterns

between

many

kinds

of

technical standards seamless cut.

UWB is also called the pulse to be radio, the modulation uses the pulse

width

in

the

nanosecond

level

fast

rise

and

the

drop

pulse,

the

pulse

cover

frequency spectrum from the cocurrent to the lucky hertz, does not need in the

radio

frequency

which

the

convention

narrow

band

frequency

modulation

needs to transform, after pulse formation, may deliver directly to the antenna

launch.

4. network security and QoS

QoS

divides

into

wireless

and

the

wired

side

two

parts,

wireless

side's

QoS involves the radio resource management and the dispatch, the admission

3

control

and

the

mobility

management

and

so

on,

the

mobility

management

mainly includes the terminal mobility, individual mobility and service mobility.

Wired side's QoS involves based on the IP diffSer discrimination service and

the RSVP end-to-end resources reservation mechanism. Mechanism maps the

wireless side IP diffSer IP the QoS. Network security including network turning

on

security,

core

network

security,

application

security,

safety

mechanism

visibility and configurable.

In the above modern mobile communication key technologies's foundation,

has

had

the

land

honeycomb

mobile

communication,

the

satellite

communication as well as the wireless Internet communication, these mailing

address

caused

the

correspondence

appearance

to

have

the

huge

change,

used

the

digital

technique

the

modern

wireless

communication

already

to

permeate the national economy each domain and people's daily life, for this

reason, we needed to care that its trend of development, hoped it developed

toward more and more convenient people's life's direction, will let now us have

a look at the modern mobile communication the future trend of development.

modern

mobile

communication

technological

development

seven

new

tendencies :

First,

mobility

management

already

from

terminal

management

to

individual management and intelligent management development

Second,

network

already

from

synchronized

digital

circuit

to

asynchronous

digital

grouping

and

asynchronous

transfer

mode

(ATM)

development;

the

three,

software's

developments

actuated

from

the

algorithm

to

the

procedure-oriented and face the goal tendency development;

the four, information processing have developed from the voice to the data

and the image;

five,

wireless

frequency

spectrum

processing

already

from

narrow

band

simulation to the narrow band CDMA development;

the

six,

computers

have

developed

from

central

processing

to

the

4