wireless communication lecture
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Wireless Communications
Dr. R P. Yadav Professor,
Electronics and Communication Department
MNIT, Jaipur
Former Vice Chancellor
Rajasthan Technical University Kota
Former Chairman
North Western Regional Council Chandigarh
AICTE
Outline
� Communication Systems
� Wireless Communications
� Current Wireless Systems
� Deteriorating factors
� Advantages/Drawbacks� Advantages/Drawbacks
� Design challenges
� Future of Wireless
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Communication Systems
Transmitter
Carrier
Transmitted
signal
Channel
Received
signal
Receiver
Information to be transmitted
(Baseband signal)
Recovery of information
3
Wireless Communications� Transfer of information without electrical conductor/optical fiber
� Radio
� Free space optical
� Sonic
� Electromagnetic induction
� There are many devices used for wireless communication� There are many devices used for wireless communication
� mobiles.
� Cordless telephones,
� satellite television
� wireless computer parts.
� Current wireless phones include
� 3G and 4G networks
� Bluetooth
� Wi-Fi technologies.4
Wireless Comes of Age
� Guglielmo Marconi invented the wireless telegraph in 1896
� Communication by encoding alphanumeric characters in analog signal
� Sent telegraphic signals across the Atlantic Ocean
� Communications satellites launched in 1960s� Communications satellites launched in 1960s
� Advances in wireless technology
� Radio, television, mobile telephone, communication satellites
� More recently
� Satellite communications, wireless networking, cellular technology
5
Current Wireless Systems
� Cellular systems
� Wireless LANs
� Satellite Systems
� Paging Systems
� Bluetooth� Bluetooth
� Infrared Communication
� Ultra wideband Radios
� Zigbee Radios
6
Wireless Systems: Range Comparison
SatelliteSWMWFMMobile
1,000 Km100 Km10 Km1 Km100 m10 m1 m
SatelliteLinksRadioRadio
FMRadioTelephonyWLANsBlueooth
7
Cellular Systems:Reuse channels to maximize capacity
• Geographic region divided into cells• Frequencies/timeslots/codes reused at spatially-separated
locations.
• Co-channel interference between same color cells.
• Base stations/MTSOs coordinate handoff and control functions
• Shrinking cell size increases capacity, as well as networking • Shrinking cell size increases capacity, as well as networking burden
BASE
STATIO
N MTSO
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Type of Cells
Satellite
UrbanIn-Building
Global
Suburban
MacrocellMicrocell
Picocell
Basic Terminal
PDA Terminal
Audio/Visual Terminal
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Contd..
• Cell radii can vary from 10s of meters in buildings to 100s of meters in the cities, up to several kms in the countryside.
• Macrocells, provide overall area coverage.
• Microcells focuses on slow moving subscribers moving • Microcells focuses on slow moving subscribers moving between buildings.
• Picocells focuses on the foyer of a theater, or exhibition centre.
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The Wireless Revolution
Cellular is the fastest growing sector of communication industry (exponential growth since 1982, with over 2 billion users worldwide today)
• Three generations of wireless
– First Generation (1G): Analog 25 or 30 KHz FM, voice only, mostly vehicular communication
– Second Generation (2G): Narrowband TDMA and CDMA, voice and low bit-rate – Second Generation (2G): Narrowband TDMA and CDMA, voice and low bit-rate data, portable units.
2.5G increased data transmission capabilities
– Third Generation (3G): Wideband TDMA and CDMA, voice and high bit-rate data, portable units
– Fourth Generation (4G): Broadband, all-IP packet switched network , dynamic sharing of resourcing, IEEE 802.6m standard plus LTE Advanced.
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How Did We Get This Far in Just 25 Years?
• Relentless progress in silicon technology� Higher integration, lower costs ($20 phones readily
available in emerging markets), more capabilities.
• Technical advances in air interfaces• Technical advances in air interfaces� Higher efficiency for voice and data services, lower
infrastructure capital costs.
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SIC Had Been Sitting on the Bookshelf…
• Until the perfect storm arrived about 3 years ago…
• Realization that sum rate capacity could be achieved without the need of synchronous transmissions and exponential power distribution
• Process technology node transitions• Process technology node transitions
• Development of embedded memory technology allowed large amounts of on-chip memory
• Thus we had the ingredients and the recipe, all that was left was a lot of hard work…
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Two Directions
• A. Continue improvements in spectral efficiency with tighter coordination amongst base stations
• B. Change the metrics: Focus on increasing density of deployment to optimize spectral density of deployment to optimize spectral efficiency/area.
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Summary
• Continued growth in cell-phone penetration.
• Emergence of new class of ‘data-centric’ wireless devices.
• Battery technology not keeping pace, but • Battery technology not keeping pace, but innovative solutions are emerging.
• Traditional optimization in wireless technology reaching its theoretical limits.
• Topology, not technology, will provide the next leap in air interface capacity.
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Wireless Local Area Networks (WLANs)
01011011
Internet
Access
Point
0101 1011
� WLANs connect “local” computers (100m range)
� Breaks data into packets
� Channel access is shared (random access)
� Backbone Internet provides best-effort service
� Poor performance in some apps (e.g. video)
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Wireless LAN Standards
• 802.11b (Current Generation)
– Standard for 2.4GHz ISM band (80 MHz)– Frequency hopped spread spectrum– 1.6-10 Mbps, 500 ft range
• 802.11a (Emerging Generation)
– Standard for 5GHz NII band (300 MHz)– OFDM with time division– OFDM with time division– 20-70 Mbps, variable range– Similar to HiperLAN in Europe
• 802.11g (New Standard)
– Standard in 2.4 GHz and 5 GHz bands– OFDM – Speeds up to 54 Mbps
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Satellite Systems
� Cover very large areas
� Different orbit heights
� GEOs (39000 Km) versus LEOs (2000 Km)
� Optimized for one-way transmission
� Radio (XM, DAB) and movie (SatTV) broadcasting
� Most two-way systems are struggling or bankrupt
� Expensive alternative to terrestrial system
� A few ambitious systems on the horizon
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Ad-hoc Networks
• Ad Hoc Network is a multi-hop relaying network
• In 1994, Bluetooth proposed by Ericsson to develop a short-range, low-power, low complexity, and inexpensive radio interface
• WLAN 802.11 spec. is proposed in 1997• WLAN 802.11 spec. is proposed in 1997
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Applications of Ad-hoc Networks
• Military Applications
� Establishing communication among a group of soldiers for tactical operations
� Coordination of military object moving at high speeds such as fleets of airplanes or ships
� Requirements: reliability, efficiency, secure communication, –Requirements: reliability, efficiency, secure communication, and multicasting routing,
• Collaborative and Distributed Computing
� Conference, distributed files sharing
• Emergency Operations
� Search, rescue, crowd control, and commando operations
� Support real-time and fault-tolerant communication paths31
Issues in Ad Hoc Wireless Networks
• Medium access scheme
• Routing, Multicasting, TPC protocol
• Pricing scheme, QoS, Self-organization
• Security, Energy management • Security, • Security, Energy management • Security, Energy management
• Addressing and service discovery
• Deployment considerations
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Medium Access Scheme
• Distributed operation• fully distributed involving minimum control overhead
• • Synchronization• Mandatory for TDMA-based systems
• Hidden terminals• Hidden terminals• Can significantly reduce the throughput of a MAC protocol
• Exposed terminals
• To improve the efficiency of the MAC protocol, the exposed nodes should be allowed to transmit in a controlled fashion without causing collision to the on-going data transfer
• • Access delay
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The Major Issues of MAC Scheme
• Throughput and access delay• To minimize the occurrence of collision, maximize channel
utilization, and minimize control overhead
• Fairness
• Equal share or weighted share of the bandwidth to all • Equal share or weighted share of the bandwidth to all competing nodes
• Real-time traffic support
• Resource reservation• Such as BW, buffer space, and processing power
• Capability for power control
• Adaptive rate control
• Use of directional antennas34
The Major Challenge of Routing Protocol
• Mobility result in frequent path break, packet collision, and difficulty in resource reservation
• Bandwidth constraint: BW is shared by every node
• Error-prone and share channel: high bit error rate
• Location-dependent contention: distributing the network • Location-dependent contention: distributing the network load uniformly across the network
• Other resource constraint: computing power, battery power, and buffer storage
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The Major Requirement of Routing Protocol
• Minimum route acquisition delay
• Quick route reconfiguration: to handle path breaks
• Loop-free routing
• Distributed routing approach
• Minimum control overhead • Minimum control overhead• Minimum control overhead • Minimum control overhead
• Scalability
• Provisioning of QoS: • supporting differentiated classes of services
• Support for time-sensitive traffic
• Security and privacy
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Quality of Service Provisioning
• QoS often requires negotiation between the host and the network, resource reservation schemes, priority scheduling and call admission control
• QoS in Ad hoc wireless networks can be on a per flow, per link, or per nodeper link, or per node
• Qos Parameters: different applications have different requirements
• Multimedia: bandwidth and delay are the key parameters
• Military: BW, delay, security and reliability
• Emergency search –and-rescue: availability is the key parameters, multiple link disjoint paths
• WSN: battery life, minimum energy consumption
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Self-Organization
• An important property that an ad hoc wireless network should exhibit is organizing and maintaining the network by itself
• Major activities: neighbour discovery, topology organization, and topology reorganizationorganization, and topology reorganization
• Ad hoc wireless networks should be able to perform self-organization quickly and efficiently
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Scalability
• The latency of path-finding involved with an on-demand routing protocol in a large ad hoc wireless network may be unacceptably high
• A hierarchical topology-based system and addressing may be more suitable for large ad-hoc wireless networksmay be more suitable for large ad-hoc wireless networks
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Deteriorating factors
Channel_
Medium through which communication is being held and as we are talking about wireless this is the radio propagation channel
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Channel provides the connectivity between transmitter and receiver but the same time it exhibits many different forms of channel impairment
Deteriorating factors
Additive Channel Impairment
o Thermal Noiseo AWGNo Reduces signal detect ability at the receiver sideo Can be compensated with high SNR
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o Can be compensated with high SNR
Multiplicative Channel Impairment
o Multipath propagation o Reduction in usable frequency spectrum
Multiplicative impairment
Frequency dispersion• Fading
• Received signal strength fluctuations
• Long term Fading
� Shadowing and variation in the distances
� Slow rate and can be compensated with Power � Slow rate and can be compensated with Power control
• Short term fading
� Multipath propogation
� Diversity and Error correction coding are used to compensate
Multiplicative impairment
Time dispersion• Inter Symbol Interference (ISI)
• Overlapping in adjacent symbol time
• Can be compensated with use of Equalisers in case of
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• Can be compensated with use of Equalisers in case of FDMA/TDMA systems and Rake receivers in case of CDMA systems
Physical Factors Influencing Fading in Mobile Radio
Channel
(MRC) � 1) Multipath Propagation
– And strength of multipath signals
– time delay of signal arrival
• large path length differences → large differences in delay between signals
– urban area with many buildings distributed over large spatial scale
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– urban area with many buildings distributed over large spatial scale
• large # of strong multipath signals with only a few having a large time delay
– suburb with nearby office park or shopping mall
• moderate # of strong multipath signals with small to moderate delay times
– rural → few multipath signals (LOS + ground reflection)
Physical Factors Influencing Fading in Mobile Radio
Channel
(MRC) � 2) Speed of Mobile
– relative motion between base station & mobile causes
random frequency modulation due to Doppler shift (fd)
– Different multipath components may have different
frequency shifts.
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frequency shifts.
� 3) Speed of Surrounding Objects
– also influence Doppler shifts on multipath signals
– dominates small-scale fading if speed of objects > mobile
speed
• otherwise ignored
Physical Factors Influencing Fading in Mobile Radio
Channel
(MRC)
� 4)Tx signal bandwidth (Bs)
– The mobile radio channel (MRC) is modeled as filter with
specific bandwidth (BW)
– The relationship between the signal BW & the MRC BW
will affect fading rates and distortion, and so will determine:
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will affect fading rates and distortion, and so will determine:
a) if small-scale fading is significant
b) if time distortion of signal leads to inter-symbol
interference (ISI)
– An MRC can cause distortion/ISI or small-scale fading, or
both.
• But typically one or the other
Short term fading Solutions DIVERSITY-
• More than one independently faded version of the transmitted
signal so that if one multipath undergoes a deep fade another
path signal may provide a strong input
� Frequency Diversity
� Time Diversity� Time Diversity
� Space Diversity
• These independently faded signal components at the output of
demodulator are combined with techniques
� Maximal Ratio Combining
� Equal gain combining
� Selective combining
Short term fading Solutions
ERROR CORRECTION CODE
� For independent symbol error
• Block length codes
• Get the coding gain with Controlled redundancy
� For Bursty error enviornment
• Correlated (Fading) channel
• Negative effect over coding gain
• Coding scheme with interleaving
• Delay
• Hardware memory units
Advantages of Wireless Communication
� Any data or information can be transmitted faster and with a high
speed
� Maintenance and installation is less cost for these networks.
� The internet can be accessed from anywhere wirelessly
� It is very helpful for workers, doctors working in remote areas as � It is very helpful for workers, doctors working in remote areas as
they can be in touch with medical centers.
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Disadvantages of Wireless Communication
� An unauthorized person can easily capture the wireless signals
which spread through the air.
� It is very important to secure the wireless network so that the
information cannot be misused by unauthorized usersinformation cannot be misused by unauthorized users
� Lack of compatibility makes it cumbersome to design and upgrade
the existing systems.
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Design Challenges
� Hardware Design
� Precise components
� Small, lightweight, low power
� Cheap
� High frequency operations
� System Design
� Converting and transferring information
� High data rates
� Robust to noise and interference
� Supports many users
� Network Design
� Connectivity and high speed
� Energy and delay constrains
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Future of wireless
� Satellite and Space communication
� Internet of things
� Communication for the smart grid
� Access system and netwok
� Wireless sensor network� Wireless sensor network
� Green Wireless Communication Design
� Wireless optical broadband access network (WOBAN)
� Next Generation Mobile Networks
� In Medical
� Implanted devices
� Remote surgery
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Top Technology Trends in 2015
1. 5G
2. FIBER EVERYWHERE
3. VIRTUALIZATION, SDN & NFV
4. EVERYWHERE CONNECTIVITY FOR IoT & IoE4. EVERYWHERE CONNECTIVITY FOR IoT & IoE
5. COGNITIVE NETWORKS, BIG DATA
6. CYBERSECURITY
7. GREEN COMMUNICATIONS
8. SMARTER SMARTPHONES, CONNECTED SENSORS
9. NETWORK NEUTRALITY, INTERNET GOVERNANCE
10.MOLECULAR COMMUNICATIONS