1. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Police Technology Police Technology Chapter Three Police Technology Wireless Communications

2. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Learning Objectives Basic radio wave theory Basic radio wave theory Analog and digital communications Analog and digital communications Basic parts of radio frequency communications Basic parts of radio frequency communications Digital communications; including Digital communications; including Time Division Multiple Access (TDMA) Time Division Multiple Access (TDMA) Frequency Division Multiple Access (FDMA) Frequency Division Multiple Access (FDMA) Code Division Multiple Access (CDMA) Code Division Multiple Access (CDMA) Cellular Digit Packet Data (CDPD) Cellular Digit Packet Data (CDPD) Cellular telephone systems Cellular telephone systems

3. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Radio Basics There are two medias for the transmission of electronic information: Information can be transmitted over a wire, like telephone conversations. Information can be transmitted over a wire, like telephone conversations. It can be transmitted through the atmosphere; wireless like the signals your car radio receives. It can be transmitted through the atmosphere; wireless like the signals your car radio receives.

4. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Radio Basics Wireless communication has an advantage over hardwired communications Wireless can be broadcast over a wide area and to a large number of users. Because wireless communication uses radio frequencies, it is often referred to as RF communication

5. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Radio Basics Radio waves are the way in which both analog and digital signals are carried as wireless Communications. Voice and data information can be carried by either. Both have advantages and disadvantages.

6. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Analog radio system consists of a microphone that modulates (changes) the human voice to an analog wave, which is processed and sent to an antenna for transmission. The return signal is passed through the antenna to be received, processed, and broadcast out a speaker Radio Basics Radio Basics

7. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Radio Basics An analog radio system can carry digital signals, but first the digital signal must be converted from its analog configuration to a digital configuration. This is accomplished by a modulator-demodulator unit, a modem. For this transmission scheme to work, both the sender and receiver must have a modem.

8. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster As you move further away from the antenna that is broadcasting an analog signal, the signal becomes weaker until the strength of the signal is lost in background static and the transmission cannot be heard. Radio Basics

9. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Radio Basics A digital signal can be broadcast only up to a certain distance. A digital signal can be broadcast only up to a certain distance. Once that distance is reached, the signal for transmission is gone Once that distance is reached, the signal for transmission is gone

10. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Radio Basics Radio signals travel in waves (like sound and light). Radio waves are like ripples in a pond with two important differences: You cannot see radio waves. They are invisible; and, You cannot see radio waves. They are invisible; and, Radio waves stay constant. They do not distant themselves (grow further apart). Radio waves stay constant. They do not distant themselves (grow further apart).

11. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Radio Basics Radio waves travel in a constant pattern. The number of wave cycles per second is called a Hertz, or more commonly the radio frequency.

12. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Radio Basics AM/FM radios work in ranges that are different from each other. AM/FM radios work in ranges that are different from each other. These ranges of frequencies are called bands. These ranges of frequencies are called bands. Different frequency bands share certain broadcast characteristics. Different frequency bands share certain broadcast characteristics.

13. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Different groups of frequencies are called channels. Different groups of frequencies are called channels. The number of frequencies in a channel is referred to as the channel’s bandwidth. The number of frequencies in a channel is referred to as the channel’s bandwidth. The more bandwidth, the more information a channel can handle. The more bandwidth, the more information a channel can handle. A guard band prevents the channels from overlapping and confusing the information exchange. A guard band prevents the channels from overlapping and confusing the information exchange. Radio Basics

14. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Effective radiated power – how far away from the source a signal can be received and interpreted. Lower frequency = Higher effective radiated power Radio Basics

15. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Radio Basics Wireless signals sent in a Very High Frequency (VHF) - many wave cycles per second - provide a wider area of coverage. Wireless signals sent in a Very High Frequency (VHF) - many wave cycles per second - provide a wider area of coverage. Shorter wavelengths of Ultra High Frequency (UHF) – even more cycles per second - go through building windows better than VHF. Shorter wavelengths of Ultra High Frequency (UHF) – even more cycles per second - go through building windows better than VHF.

16. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Frequencies within a band share a propensity to skip. Skip occurs when a broadcast reflects off the Earth’s ionosphere. Frequencies within a band share a propensity to skip. Skip occurs when a broadcast reflects off the Earth’s ionosphere. Noise and interference more of a problem for lower frequencies (like AM radio) Noise and interference more of a problem for lower frequencies (like AM radio) The larger the frequency, the larger the antenna required. The larger the frequency, the larger the antenna required. Radio Basics

17. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Communications Hardware Basics Transmitter - generates radio wave Transmitter - generates radio wave (the signal) Receiver - receives signal, changes it back into the original form Receiver - receives signal, changes it back into the original form Transceiver - combination of both Transceiver - combination of both

18. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Job of transmitter is to generate the signal. Job of transmitter is to generate the signal. That frequency is a series of oscillating waves. Oscillation means the waves peak and valley in a predictable and uniform manner. That frequency is a series of oscillating waves. Oscillation means the waves peak and valley in a predictable and uniform manner. The part of the transmitter that generates these waves is the oscillator. The part of the transmitter that generates these waves is the oscillator. Communications Hardware Basics

19. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster To transmit data we use the Frequency Shift Key (FSK) method – two separate frequencies are used to represent ones and zeros of binary data. To change voice into digital we use a voice coder (vocoder) – the reverse of a modem. Communications Hardware Basics

20. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Different antennas have different propagation characteristics (the way the antenna sends out the signal. Different antennas have different propagation characteristics (the way the antenna sends out the signal. Basic antenna is a dipole (straight wire or metal). Basic antenna is a dipole (straight wire or metal). Communications Hardware Basics

21. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Communications Hardware Basics You can increase the range of transmission by adjusting the gain - directing the antenna’s radiating energy in alternate directions.

22. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Simple Voice (simplex system) - Users transmit and receive information on a single channel or frequency. Simple Voice (simplex system) - Users transmit and receive information on a single channel or frequency. Repeater System – The signal is picked up by a repeating antenna and repeated at a higher point and on another frequency to base. Repeater System – The signal is picked up by a repeating antenna and repeated at a higher point and on another frequency to base. Trunked Radio System – locates an empty line and assigns it to the user for the duration of the transmission Trunked Radio System – locates an empty line and assigns it to the user for the duration of the transmission Radio Frequency Systems

23. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Frequency Division Multiple Access Increases spectrum efficiency Increases spectrum efficiency Typical frequency of 30 kHz is divided into three channels of 10 kHz each. Typical frequency of 30 kHz is divided into three channels of 10 kHz each. Increases the number of frequencies that can be used in conjunction with a trunked radio system. Increases the number of frequencies that can be used in conjunction with a trunked radio system.

24. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster TDMA takes advantage of the space between words. TDMA takes advantage of the space between words. Each user is allowed a small portion of the broadcast cycle. Each user is allowed a small portion of the broadcast cycle. Timed to not interfere with each other. Timed to not interfere with each other. Time Division Multiple Access

25. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Code Division Multiple Access In CDMA, each transmission of digital information is spread out among all of the available channels. In CDMA, each transmission of digital information is spread out among all of the available channels. The digital frames move from one frequency to the next in milliseconds. The digital frames move from one frequency to the next in milliseconds. The frames must be put back together with a unique code (direct sequence) to each call. The frames must be put back together with a unique code (direct sequence) to each call.

26. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Cellular Technology Cell Site – a physical location that contains a cellular telephone antenna array and a base station controller. Cell Site – a physical location that contains a cellular telephone antenna array and a base station controller. Cell is the area of coverage provided by the cell site antenna array. Cell is the area of coverage provided by the cell site antenna array.

27. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Cellular Technology The configuration of cell sites has some of the same characteristics of the repeater antenna configuration. The configuration of cell sites has some of the same characteristics of the repeater antenna configuration. A primary characteristic that identifies a cellular system is frequency reuse. A primary characteristic that identifies a cellular system is frequency reuse. A primary characteristic of cellular technology is the ability hand signals off from cell to cell. A primary characteristic of cellular technology is the ability hand signals off from cell to cell.

28. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Cellular Digit Packet Data CDPD is a data network, no voice. CDPD is a data network, no voice. It has an IP address, not a telephone # It has an IP address, not a telephone # Information from a CDPD system is relayed like a cellular telephone call through a commercial carrier. Information from a CDPD system is relayed like a cellular telephone call through a commercial carrier. The subscriber pays only for the packets of data sent over the network The subscriber pays only for the packets of data sent over the network

29. Copyright 2005 - 2009: Hi Tech Criminal Justice, Raymond E. Foster Police Technology To Learn more about Leadership visit Leadership www.pokerleadership.com