CS 898T Mobile and Wireless Networks - Homework 1 - Name:_________________ Assigned: Monday, February 9 Due: Monday, February 16 (in class) Please show all work on a separate sheet attached to this sheet. For each question write key points. (50 points - 10 points for each question) 1. Based on mobility and wirelessness catogorize communication devices and give an example for each catogory. Ans: Based on the mobility and wireless ness, the communication devices can be categorized into the following: 1) Fixed and Wired Networks. eg. Desktop connected to a home/office LAN. 2) Mobile and Wired Networks. eg. Laptop. 3) Fixed and Wireless: - eg. Used for installing networks in historical buildings etc. 4) Mobile and Wireless. eg. Mobile Phones. 2. Survey at least three operating systems for mobile phones and list their features. Select one you will use and explain why. Ans: 1) Linux OS Motorola A760 Features: o full multitasking o GNU software support o the capabilities of a personal digital assistant (PDA) o advanced messaging o instant Internet access and Bluetooth wireless technology 2) Symbian OS Sony Ericsson P900, Nokia 6600, Nokia N-Gage, Nokia 3660/3620 FOMA F2102V, FOMA F2051, Sony Ericsson P800, Nokia 7650 Nokia 3650/3600, Nokia 9290 Communicator, Nokia 9210 Communicators Motorola A920, FOMA F900i, Nokia 6620, Nokia 7700, Sendo X BenQ P30, Samsung SGH-D700, Siemens SX1 Features: The major new features of Symbian OS v7.0s are: o lightweight multi-threaded multimedia framework o support for W-CDMA o Java MIDP 2.0 o support for multiple primary/secondary PDP contexts o support for bi-directional text (Thai, Arabic and Hebrew) 3) Palm OS Developed by PalmOne, Inc. Samsung SPH-i500, Tungsten, Treo 600 Features: o Built-in Personal Information Manager (PIM) programs o Work with a PC o One-tap ease of use o Wired and wireless communication 4) Windows Mobile Developed by Microsoft Corporation Samsung i600, Motorola MPx200 Features: o Personal information management o Pocket outlook o Mobile E-mail o MSN Mobile o Web browser References: [1] http://linuxphones.com/ [2] http://www.symbian.com/ [2] http://www.palm.com/ [4] http://www.microsoft.com/windowsmobile/default.mspx 3. Survey at last three mobile phone communication standards and list their features. For each standard find a company which uses that standard. Which mobile phone communication standard is the current market leader and how much percentage does it occupy the world market? Ans: The three mobile phone communication standards with their features are as follows : See Table 2.1 Page 28 of Textbook. 1) GSM : GSM or Global System for Mobile Communications 2) CDMA 3) PDC 4) TDMA 5) UMTS (FDD) 6) AMPS 7) W-CDMA The current leader in World market is GSM with a market percentage of 73% approx at the end of year 2003. Reference: http://www.gsmworld.com 4. Describe 4 multiplexing techniques in wireless communication. Give an example for each technique. Ans: The 4 multiplexing techniques used in wireless communication are: 1) Space division multiplexing. Space division multiplexing: In wireless communication, a SDM implies a separate sender for each communication channel with wide enough distance between senders. For example, This type of multiplexing is used at FM radio stations where the transmission range is limited to a certain region. Many radio stations around the world can use the same frequency without interference. 2) Time division multiplexing. Time division multiplexing: This is a more robust and flexible multiplexing scheme. Here a particular channel is given the whole bandwidth for a certain amount of time i.e. all senders senders use the same frequency but in different points in time. There might be a co-channel interference and to avoid it, precise synchronization between senders is necessary. For example, The mobile phone GSM standard uses this combination of frequency and time division multiplexing for transmission between mobile phones and base stations. 3) Frequency division multiplexing. Frequency division multiplexing: This method describes schemes to subdivide the frequency dimension into several non-overlapping frequency bands. Senders using a certain frequency band can use this band continuously. This is a very simple type of multiplexing that does not require coordination between the sender and the receiver. Example, This scheme is used for radio stations within the same region, where each radio station has its own frequency. 4) Code division multiplexing. Code division multiplexing: This is a relatively new scheme and was first used in military applications due to inherent security features. All channels use the same frequency at the same time for transmission. By using a secret code or a language, a secure channel can be established. Thus, the receiver can still receive the information but if the language is unknown, then the information is useless. This also provides good security again tapping and interference. The code space being bigger than frequency space. For example, voice signals and military applications for security. 5. What is digital modulation? Why is digital modulation required? Describe three basic digital modulation methods? What is analog modulation? Why cannot the baseband signal be directly transmitted in a wireless system? Ans: Digital Modulation : The digital data (0 and 1) is translated into an analog signal (baseband signal). Digital modulation is required if digital data has to be transmitted over a medium that only allows for analog transmission. The three basic digital modulation methods are : 1) Amplitude shift keying (ASK) Amplitude shift keying is the most simple of the digital modulation techniques. The two digital values 0 and 1 are represented by 2 different amplitudes. 2) Phase shift keying (PSK) Phase shift keying uses shifts in the phase of a signal to represent data. A phase shift of 180 or pi as 0 follows 1 and vice versa. 3) Frequency shift keying (FSK) Frequency shift keying is the often used method in wireless transmission. The simplest form, binary FSK assigns one frequency F1 to 1 and another frequency F2 to 0. The oscillators can be switched depending on the input to implement FSK. Analog Modulation: Analog modulation shifts the center frequency of the baseband signal generated by the digital signal up to the radio carrier. There are 3 main reasons why a baseband signal cannot be directly transmitted in a wireless system. 1) Antennas: An antenna must be the order of magnitude of the wavelength signal in size to be effective. 2) Frequency division multiplexing: Using only baseband transmission, FDM could not be applied. 3) Medium characteristics: Path loss, penetration of obstacles, reflection, scattering and diffraction. All the effects depend on the wavelength of a signal.