Cdma frequency reuse pdf

It is 1k or k according to some books where k is the number of cells which cannot use the same frequencies for transmission. Capacity in cdma is soft, cdma has all users on each frequency and users are separated by code. Time division synchronous code division multiple access chinese 3g 3. Gsm and cdma spectrum frequencies the cdma network operates in the frequency spectrum of cdma 850 mhz and 1900 mhz while the gsm network operates in the frequency spectrum of gsm 850 mhz and 1900 mhz. The concept of regular frequency reuse patterns is also used for broadcast transmitters. Core network pstn pstn pstn, packet network packet network ip network internet 8. Frequency reuse applied to cdma channels in a cellular system. Fcc allocated radio spectrum throughout the carriers market. Pdf frequency reuse scheme for cellular ofdm systems. Cdma requires a tight power control, as it suffers from nearfar effect. The bandwidth of the coded data signal is chosen to be much larger. So, cdma capacity calculations should be very simple.

Universal frequency reuse frequency reuse cluster size k 1 simple planning large capacity increase telcom 2720 6 c b d f g e a c b d f g e a c b d f g e a universal frequency reuse a a a a a a a a a a a a a a a a a a a a a frequency reuse factor 7 for amps cc bb dd ee aa ff gg cdma universal frequency reuse frequency reuse. Cdma field trials are currently underway by major cellular and personal communications companies using existing cellular spectrum in the 800900 mhz and 1. For example, consider a 1 x 1 x 3 frequency reuse pattern. In radio broadcasting, a similar concept has been developed based on rhombic cells. Coverage of cellular telephone systems by the year 2000. Abstractthe downlink performance of cellular networks is known to be. This means, cdma operates in the presence of noise and interference. The frequencies used in different cells must be planned carefully to ensure signals from different cells do not interfere with each other. The virtues of spread spectrum in a frequency reuse mobile radio environment have. It plays the same role in the cdma capacity equation 11 that the narrowband frequency reuse factor k does in amps capacity. Effects of radio propagation path loss on dscdma cellular. Qualcomm paper claimed that due to voice activity, frequency reuse, and sectorization, cdma increased capacity by. Channel reuse strategies for indoor infrared wireless communications 1281 fig. The greater the number of codes, the more the number of users.

Principles of cellular frequency reuse in the cellular concept, frequencies allocated to the service are reused in a regular pattern of areas, called cells, each covered by one base station. In addition, neighboring cells use the same frequencies, which means no reuse. Frequency reuse frequency reuse is the core concept of cellular mobile radio. The proposed ds cdma fdma cellular system implements frequency reuse with a novel cell configuration to decrease cochannel interference. Frequency reuse is the ability to reuse the same radio channel frequency at other cell sites within a cellular system. Concept of frequency reuse channels cellular network. What is frequency reuse and resource block reuse in lte.

Pdf flexible design of frequency reuse factor in ofdma. In the cellular reuse concept, frequencies allocated to the service are reused in a regular pattern of areas, called cells, each covered. Wideband code division multiple access wcdma is one of the popular air interface technologies for the third generation rf cellular communications systems. To understand the cellular frequency reuse concept ful lling the following objectives. In the cellular reuse concept, frequencies allocated to the service are reused in a regular pattern of areas, called cells, each covered by one base station. In the fdma and tdma systems, frequency planning is an important consideration. Code division multiple access for wireless communications. Comparing the capacity of tdmafdma cdma is very controversial in 1991, a famous notorious.

Code division multiple access cdma user 1 time frequency users share bandwidth by using code sequences that are orthogonal to each other some second generation systems use cdma most of third generation systems use cdma user 2 user n code. There was an estimated,000,000 users of cellular phones in the u. D minimum distance between centers of cells that use the same band of frequencies called cochannels. Nov 24, 2019 cdma, which stands for code division multiple access, is a competing cell phone service technology to gsm, on 2g and 3g networks that is gradually phasing out. This range of frequency reuse represents a number of sites in a template reuse, the number of sectors in each site, and the number of channels on the site. Then, to evaluate the effect of frequency reuse on the probability of coverage and the average. In this chapter, we turn to a network of many mobile users interested in communicating with a common. Frequency reuse drastically increases user capacity and spectrum efficiency.

In mobiletelephone nets these cells are usually hexagonal. Concept of frequency reuse channels free download as powerpoint presentation. Neighboring cells uses disjoint sets of subchannels. Tdma, cdma, gsm,pdc gprs, edge wcdma, cdma2000 single standard bandwidth 1. Creating multiple data channels, they can support the flexible frequency reuse factor. Using a separate frequency band is a form of fdd frequency division duplexing. Frequency reuse scheme for cellular ofdm systems article pdf available in electronics letters 388. Frequency reusethe increased capacity in a cellular network, comparing to a network with a singletransmitter, comes from the fact that the same radio frequency can be reused in adifferent area for a completely different transmission. Frequency reuse optimization for ofdma network article pdf available in journal of engineering and applied sciences 144. Local area network utilizing infrared wireless access to a wired backbone. Cdma established the foundation for 3g technologies is95 cdmaone initial cdma standard from qualcomm may 1995 mobile 3g evolved into two competing standards both based on cdma cdma2000 uses 1. In other words, a user near the base station transmitting with. Cellular phone networks use cellular frequency reuse. In this system, the cells operate asynchronously, hence it makes the mobile synchronization more complex, but offers the advantage of.

Code division multiple access or cdma has its roots in wwii era spread spectrum technology. An omnidirectional cdma cell, even with othercell interference, has a higher capacity than an amps cell by a factor of kf 71. Types of channels control channel forward downlink control channel. The frequency reuse factor is the rate at which the same frequency can be used in the network. This implementation of cdma fdma increases cell capacity above the amps type implementation of frequency reuse in a cdma system. Objective is to reuse frequency in nearby cells o 10 to 50 frequencies.

Careful frequency planning essential no intercell interference. Cdma can be implemented in several ways, two of which are frequency hopping and direct sequencing. Finding the cell clusters within certain geographic area. A frequency reuse plan is defined as how radio frequency rf engineers subdivide and assign the. Channel reuse strategies for indoor infrared wireless. On the contrary, it is crucial to the very high spectral efficiency that is the hallmark of cdma. Frequency reuse in mobile communication systems a slot of a carrier frequency code in a carrier frequency is a radio. Adjacent cells assigned different frequencies to avoid interference or crosstalk. To understand the cellular frequency reuse concept fulfilling the following objectives. Real cells are not perfectly hexagonal, but rather depend on thesurface contour. Cdma is altering the face of cellular and pcs communication by. From equation 11, it is evident why we call f the effective frequency reuse factor.

Factor of 18 relative to amps factor of 6 relative to us tdma and similar for gsm this turned out to be optimistic, about of this gain. Cellular frequency reuse patternscellular frequency reuse patterns fdma reuse cdma reuse 1 1 1 1 1 1 1 1 1 1 3 6 2 6 2. Other discussions in these pages show why this is true. The receiver, knowing the code sequence of the user, decodes the received signal and recovers the original data. Examples of systems using cellular frequency reuse are gsm and amps. Fundamentals of communications access technologies. In 1985, the fcc allocated three frequency bands to spread spectrum communications. Users in different geographical areas in different cells may simultaneously use the same frequency. Unlike the fdmtdma cellular systems discussed in chapter 4, cdma cellular systems are based on the principle of universal frequency reuse.

Analytical performance evaluation of various frequency reuse and. One example is the planning of local 30 watt radio stations in the netherlands and belgium. Fdma and tdma usually need reuse factors of 4 7 capacity increased 47 fold. If a user doesnt have anything to send, the time frequency slot allocated to them is wasted. Cellular concept and frequency reuse in adc kpr blog.