Podcast
Questions and Answers
What is one of the main features that distinguishes 4G from its predecessor?
What is one of the main features that distinguishes 4G from its predecessor?
Which technology is NOT mentioned as part of the 4G enabling technology?
Which technology is NOT mentioned as part of the 4G enabling technology?
What is the expected data rate for downlink in 4G networks?
What is the expected data rate for downlink in 4G networks?
Which of the following features is associated with 4G networks?
Which of the following features is associated with 4G networks?
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Which technology is used to improve wireless performance in 4G networks?
Which technology is used to improve wireless performance in 4G networks?
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What is the primary purpose of assigning different frequencies to adjacent cells in a cellular network?
What is the primary purpose of assigning different frequencies to adjacent cells in a cellular network?
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In the context of cellular networks, what does the reuse factor indicate?
In the context of cellular networks, what does the reuse factor indicate?
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How are cellular areas typically organized to optimize frequency reuse?
How are cellular areas typically organized to optimize frequency reuse?
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What role does the base station play in a cellular network?
What role does the base station play in a cellular network?
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Which of the following statements about frequency allocation in cellular networks is correct?
Which of the following statements about frequency allocation in cellular networks is correct?
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What technology do both WiMAX and LTE utilize to achieve high data rates?
What technology do both WiMAX and LTE utilize to achieve high data rates?
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Which of the following is a distinct feature of LTE compared to WiMAX?
Which of the following is a distinct feature of LTE compared to WiMAX?
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What is one advantage that WiMAX holds over LTE?
What is one advantage that WiMAX holds over LTE?
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Which layer of the communication stack does the GTP-U protocol primarily operate in?
Which layer of the communication stack does the GTP-U protocol primarily operate in?
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Which of the following describes a function of Frequency Reuse in cellular networks?
Which of the following describes a function of Frequency Reuse in cellular networks?
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In terms of data flow, what is an advantage of using Mobile WiMAX?
In terms of data flow, what is an advantage of using Mobile WiMAX?
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Which generation of cellular systems includes GSM and IS-95?
Which generation of cellular systems includes GSM and IS-95?
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What key aspect is primarily managed by the Relay section in the communication architecture?
What key aspect is primarily managed by the Relay section in the communication architecture?
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Study Notes
Wireless Mobile & Multimedia Networking (7COM1076)
- Course covers Cellular Wireless Networks
- Topics include Principles of Cellular Networks, AMPS (1G), GSM (2G TDMA) and IS-95 (2G CDMA), WiMax and LTE (both 4G OFDM).
Evolution of Cellular Wireless Systems
- Shows a table illustrating the evolution of cellular wireless systems, including generations (1G-4G)
- Generations are defined by data rate capabilities: 1G ≤ 10 kbps, 2G 9.6-64 kbps, 2.5G 64-144 kbps, 3G 384 kbps-2 Mbps, evolved 3G 384 kbps - 20 Mbps, 4G >20 Mbps
- System progression from AMPS to GSM, cdma2000, and WCDMA to today's technologies
Cellular Network Organization
- Designed using multiple low-power transmitters (less than 100W).
- Divided into cells serviced by individual base stations (BSS)
- BSS include transmitter, receiver and a control unit.
- Cells allocated frequency bands ensuring non-overlapping and adjacent cells operate using different frequencies to avoid interference
Frequency Reuse Patterns
- Frequency reuse patterns (N=4 and N=7) are shown
- Patterns illustrate how cells are spaced to use the same bands of frequencies.
- The distance between cells using the same frequency is determined by the reuse factor (N).
Frequency Reuse
- Adjacent cells use different frequencies to prevent interference.
- Goal: Reuse frequencies in nearby cells to optimize the use of the spectrum
- Transmission power is controlled to limit interference with adjacent cells
- Crucial factor for determining how many cells are needed between two using the same frequency
Reuse Factor
- Defines the minimum distance between cells using the same frequency band (cochannels).
- Uses a hexagonal pattern to represent cells.
- The reuse factor (N) is the number of cells in the pattern using a unique set of frequencies
- Formulas to determine D/R and D/d are given (D/R = sqrt(3N), D/d = sqrt(N))
Approaches to Cope with Increasing Capacity
- Adding new channels
- Frequency borrowing- using frequencies from adjacent cells to increase capacity.
- Cell splitting- dividing congested cells into smaller cells for increased capacity.
- Cell sectoring- dividing cells into sectors, each assigned specialized channels to reduce interference.
- Microcells- using smaller antennas positioned strategically for better coverage.
Cellular System Overview
- Diagram shows the components of a cellular system, including the public switched telecommunication network (PSTN), mobile telecommunication switching office (MTSO) and base transceiver stations (BTS).
- The system interconnects mobile units, transmitting and receiving data.
Cellular Systems Terms
- Base Station (BS): Includes antenna, a control unit, and receiver units.
- Mobile Telecommunication Switching Office (MTSO): Connects calls between mobile units.
- Two types of channels exist in the system:
Control channels: Used to exchange information between mobile units and base stations (BSS)/MTSO and setting up and maintaining calls Traffic Channels: Carry voice or data connections between users
Steps in an MTSO Controlled Call between Mobile Users
- Steps in call initiation, from mobile unit initialization to call acceptance/handoff and call termination
- Diagrams illustrate cell selection, paging and handoff.
Additional Functions in an MTSO Controlled Call
- Call blocking (busy, interference, weak signal)—functions limiting calls if an issue occurs
- Termination related functionality (hang-up, call drop)
Handoff Performance Metrics
- Cell blocking probability-Probability of new call being blocked
- Call dropping probability-Probability of terminating a call due to a handoff
- Call completion probability-Probability that a call is not dropped before termination
- Probability of unsuccessful handoff-Probability a handoff is executed with insufficient conditions
- Handoff blocking probability-Probability handoff is not successfully implemented
- Handoff probability-The probability a handoff occurs before call termination
- Rate of handoff-Number of handoffs per unit of time.
- Hard and soft handoffs (different types of handover)
Power Control
- Design issues demanding dynamic power control in a cellular system
- Received power should be higher than background noise for efficient communication.
- Minimizing transmitted power from the mobile to reduce interference and better battery use.
Advanced Mobile Phone Service (AMPS)
- Details the 25MHz bands allocated to AMPS along with the frequency channels for transmission from base to mobile and mobile to base respectively
AMPS operation
- Explains the process a subscriber takes to initiate a call using a telephone, verifies the number, and initiates calls by sending messages, ringing signals, circuit establishment, billing information and call termination
GSM Radio Link Aspects
- Explains how the 25MHz bands are divided into radio frequency carriers for GSM.
- Explains the divisions and logical channels within 25MHz bands.
GSM Frame Format
- Diagram of the GSM frame format emphasizing time slots, and encrypted bits.
IS-95
- Describes it as the most widely used second-generation CDMA (Code Division Multiple Access) system
- Utilizes Direct Sequence Spread Spectrum (DSSS) for forward and reverse (both directions) links.
- Uses chipping codes to differentiate between channels.
- Chipping codes have 64 orthogonal 64-bit codes used for the forward channel.
- Chipping codes in the reverse channel are not always guaranteed to be orthogonal.
- Orthogonality of signals is attained via orthogonal modulation.
IS-95 Radio Link Aspects
- IS-95's 25MHz frequency bands and division into 20 RF carrier channels with data every 1250KHz being further divided into 64 or 94 channels.
IS-95 Channel Structure
- Diagram showing the forward and reverse channels including pilot, paging, traffic and access channels along with the distinct long code and user-specific long code
Advantages of CDMA Cellular
- Frequency diversity (less impairment)
- Multipath resistance (reduction in interference)
- Privacy (spread spectrum with noise-like signals)
- Graceful degradation (system performance gradually declines if too many users access)
Third-Generation Capabilities
- An adaptive interface to the Internet to improve efficiency due to inbound and outbound traffic asymmetry (Internet traffic is not always symmetrical).
- More efficient use of the available spectrum in general.
- Support for a wide variety of mobile equipment
- Flexibility to allow introduction of new services and technologies.
Why 4G?
- Comparison table differentiating current services with 4G services on mobile. (e.g., Voice communication to VoIP, Internet Browsing to Super-Fast Internet)
Technical Requirements
- Required higher data rates (100 Mbps downlink, 50 Mbps uplink)
- Necessary to improve wireless reception for better coverage and to increase spectrum efficiency for more subscribers.
- High flexibility in accommodating dynamic data rates depending on subscriber need.
4G Enabling Technology
- Key technologies enabling 4G; e.g., OFDM, OFDMA, SC-FDMA, Adaptive coding and modulation (ACM), Multiple-In-Multiple-Out (MIMO) antenna processing, Turbo coding and decoding, and fighting fading channels
WiMAX vs LTE
- Overview of WiMAX's IP-based wireless broadband access technology with QoS and cellular backing, and LTE's late-starting favorite cellular technology for comparison with WiMAX and advantages of each technology.
WiMAX introduction
- Highlights the need for extending Wi-Fi range and describes WiMAX as a technology extending Wi-Fi-like services and the advantages of the use of inexpensive components and efficient frequency reuse.
- Gives details on the roles of the working group (and Roger Marks) and the combined cellular range and Wi-Fi speed.
WiMAX standards
- Outline different standards for wireless MAN air interface (802.16a, 802.16d, 802.16e, 802.16j).
- Describes development features like the addition of mobility factor, multihop relay and higher data rates.
WiMAX architecture
- Diagrammatic view of WiMAX architecture detailing the Components, such as access devices, radio access, aggregation and edge, connectivity services network, service exchange frameworks, service applications, and external networks, Core network components & data flow structure.
LTE explained
- LTE's evolution from 3rd-generation technology
- Supports higher peak data rates via wider bandwidth
- Provides low latency for faster data transmission
- Implements channel quality scheduling.
- Discusses IP based network, spectrum flexibility, improved power efficiency, and mobility support.
LTE architecture
- Highlights the components and connections in an LTE network, such as local IP connectivity, RNC, gateways, and the LTE RAN.
LTE specifications
- Describes LTE's specifications including peak data rates (downlink, uplink)
- Emphasizes latency improvement
- Supports various bandwidths
- Specifying the use of different multiplexing schemes(FDD, TDD) and the use of advanced modulation and coding schemes for uplink and downlink
Similarities
- Common features and technologies between WiMAX and LTE
Differences
- Key differences between WiMAX and LTE, including subcarrier spacing, latency, channel utilization, FFT, evolution and duplexing method, power consumption, and uplink signaling.
Comparing the End-to-End Network
- Diagrams illustrating the end-to-end network (LTE and Mobile WiMAX)
- Highlights the application, protocols and layers of each system
Comparison
- Summary comparison of LTE and WiMAX, covering their similarities and key differences.
Summary
- Comprehensive summary of the different cellular generations and networks and their technologies (e.g., FDMA, TDMA, CDMA) and other technologies like MIMO and OFDM
References
- List of referenced materials provided for the student.
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Description
This quiz covers the principles of cellular wireless networks, exploring the evolution from 1G to 4G technologies. Topics include AMPS, GSM, IS-95, WiMax, and LTE, along with network organization and frequency reuse strategies. Test your knowledge on the key concepts of mobile networking and its advancements.
