... understood orthogonal access techniques such as time divisionmultipleaccess and frequencydivisionmultipleaccess Additionally, random access schemes such as carrier sense multipleaccess are examined ... contention-free multipleaccess is in how the channels are defined In time divisionmultipleaccess (TDMA), channels are defined according to time slots In frequencydivisionmultipleaccess (FDMA) , channels ... Techniques for Code DivisionMultipleAccess 23 2.1 Forms of Code DivisionMultipleAccess 23 2.2 Direct Sequence Code DivisionMultipleAccess ...
... Techniques for Code DivisionMultipleAccess In the previous chapter, we reviewed the basic concepts of multiuser communications and the multipleaccess techniques used to allow multiple users to ... IML September 28, 2006 15:54 CODE DIVISIONMULTIPLEACCESS (CDMA) 1.2.1 ALOHA The most common contention-based methods are random access methods The first random access method was developed by Abramson ... application to ultra-wideband (UWB) systems 2.1 FORMS OF CODE DIVISIONMULTIPLEACCESS CDMA is also known as spread spectrum multipleaccess or SSMA because the use of spread spectrum waveforms...
... 28, 2006 15:54 CODE DIVISIONMULTIPLEACCESS (CDMA) FIGURE 2.4: Comparison of original/despread signal and spread signal spectra for DS/SS with square pulses 2.2.2 MultipleAccess The DS/SS technique ... MOBK023-Buehrer.cls September 28, 2006 15:54 CODE DIVISIONMULTIPLEACCESS (CDMA) Frequency 38 BS B Ts Tc Tb Time FIGURE 2.10: Example of a time frequency plot for slow hopping (Tc : hop period, ... September 28, 2006 15:54 SPREAD SPECTRUM TECHNIQUES FOR CODE DIVISIONMULTIPLEACCESS 41 If we choose the frequency spacing to be an integer multiple of the hop rate for illustration purposes, we sample...
... hopping to be incorporated into the coding decision statistics 2.8 MULTIPLEACCESS PERFORMANCE OF FREQUENCY- HOPPED CODE DIVISIONMULTIPLEACCESS Although the emphasis of this chapter is DS-CDMA, we ... additional channel estimation, which can be substantial 2.6 MULTIPLEACCESS PERFORMANCE OF DIRECT SEQUENCE CODE DIVISIONMULTIPLEACCESS The previous section examined the performance of a single ... that we have not considered that arise in the multiple cell scenario P2: IML MOBK023-Buehrer.cls September 28, 2006 15:54 CODE DIVISIONMULTIPLEACCESS (CDMA) 10 K=1 K = 10 K = 20 K = 30 K =...
... CODE DIVISIONMULTIPLEACCESS In this section, we will discuss four key principles of CDMA systems, particularly cellular systems: interference averaging, statistical multiplexing, universal frequency ... as in FDMA P1: IML/FFX MOBK023-03 P2: IML MOBK023-Buehrer.cls 78 September 28, 2006 15:55 CODE DIVISIONMULTIPLEACCESS (CDMA) One of the primary advantages of CDMA systems is universal frequency ... 28, 2006 15:55 CODE DIVISIONMULTIPLEACCESS (CDMA) 3.1.4 Statistical Multiplexing The final fundamental CDMA concept that we will discuss in this section is termed statistical multiplexing, which...
... P1: IML/FFX MOBK023-03 P2: IML MOBK023-Buehrer.cls 88 September 28, 2006 15:55 CODE DIVISIONMULTIPLEACCESS (CDMA) where I0 includes thermal noise power spectral density Including the effect ... IML/FFX MOBK023-03 P2: IML MOBK023-Buehrer.cls September 28, 2006 15:55 CELLULAR CODE DIVISIONMULTIPLEACCESS 89 Sector interference sources rm ro FIGURE 3.7: Illustration of out-of-cell interference ... (3.38) P1: IML/FFX MOBK023-03 P2: IML MOBK023-Buehrer.cls 90 September 28, 2006 15:55 CODE DIVISIONMULTIPLEACCESS (CDMA) In a similar fashion, we can show that var I P dm = · 1− Q 2κ e [σ ln(10)/10]2...
... 28, 2006 15:55 CELLULAR CODE DIVISIONMULTIPLEACCESS 3.4.3 107 Admission Control Unlike TDMA /FDMA systems, CDMA systems have a soft capacity limit That is, TDMA /FDMA systems have a specific number ... ALOHA, CSMA, and busy tone multipleaccess (BTMA) [43] Note that unlike traditional narrowband random access protocols, channel access strategies for SS/PRNs allow for multiple simultaneous transmissions ... MOBK023-Buehrer.cls 118 September 28, 2006 15:55 CODE DIVISIONMULTIPLEACCESS (CDMA) indicator of the success or failure of packet access since multiple transmissions are possible Simply sensing...
... September 28, 2006 15:56 CODE DIVISIONMULTIPLEACCESS (CDMA) The decorrelator can also be extended to non-AWGN channels For example, the receiver can be used in flat and frequency selective Rician ... be P1: IML/FFX MOBK023-05 P2: IML MOBK023-Buehrer.cls 128 September 28, 2006 15:56 CODE DIVISIONMULTIPLEACCESS (CDMA) represented as K s k (t − τk ) + n(t) r (t) = (5.1) k=1 where K users are ... first P1: IML/FFX MOBK023-05 P2: IML MOBK023-Buehrer.cls 130 September 28, 2006 15:56 CODE DIVISIONMULTIPLEACCESS (CDMA) addressed by Schneider [56] for both the synchronous and asynchronous AWGN...
... P1: IML/FFX MOBK023-05 P2: IML MOBK023-Buehrer.cls 148 September 28, 2006 15:56 CODE DIVISIONMULTIPLEACCESS (CDMA) b Matched filter User - Σ+ - Matched filter User b1 - + Σ - Matched filter ... cancellation) P1: IML/FFX MOBK023-05 P2: IML MOBK023-Buehrer.cls 150 September 28, 2006 15:56 CODE DIVISIONMULTIPLEACCESS (CDMA) Mathematically, we can represent the bit decisions for an S-stage parallel ... (5.79) P1: IML/FFX MOBK023-05 P2: IML MOBK023-Buehrer.cls 152 September 28, 2006 15:56 CODE DIVISIONMULTIPLEACCESS (CDMA) Now, if the estimates of b are correct we have ˆ ˆ Pr b = −1 | b = 1, b =...
... 17:14 CODE DIVISIONMULTIPLEACCESS (CDMA) [14] F A Tobagi and L Kleinrock, “Packet switching in radio channels: Part III—Polling and (dynamic) split-channel reservation multiple access, ” IEEE ... random -access packet switched code divisionmultipleaccess channels,” IEEE Transactions on Communications, vol 29, pp 895–901, June 1981 [46] M Joa-Ng and I Lu, “Spread spectrum medium access ... Data Communications, pp 39–49, 1997 [17] Z J Haas and J Deng, “Dual busy tone multipleaccess (DBTMA)—a multipleaccess control scheme for ad hoc networks,” IEEE Transactions on Communications,...
... understood orthogonal access techniques such as time divisionmultipleaccess and frequencydivisionmultipleaccess Additionally, random access schemes such as carrier sense multipleaccess are examined ... contention-free multipleaccess is in how the channels are defined In time divisionmultipleaccess (TDMA), channels are defined according to time slots In frequencydivisionmultipleaccess (FDMA) , channels ... Techniques for Code DivisionMultipleAccess 23 2.1 Forms of Code DivisionMultipleAccess 23 2.2 Direct Sequence Code DivisionMultipleAccess ...
... tốc độ mạng không Có tới 62% số mạng có tốc độ download cao 3,6 MB/giây, có 21% số mạng đạt 7,2 MB/giây GSA cho rằng, phát triển mạng 3,5G ảnh hưởng đến dịch vụ băng tần toàn cầu, nhiều nhà mạng ... lên tới 3.6 Mbit/giây”, song số đạt điều kiện lý tưởng Do vậy, tốc độ đường truyền không nhanh mong đợi, đặc biệt điều kiện phòng kín Tình hình triển khai HSDPA Theo số liệu Nghiệp đoàn di động ... (GSA) công nghệ 3,5G (HSDPA) chiếm đến 69% tổng số mạng di động toàn cầu Nếu 2006, có 166 mạng di động hỗ trợ HSDPA 75 nước, kết thúc năm 2007, số nhà mạng sử dụng công nghệ 204, 89 quốc gia Các...
... channel actually consists of two simplex channels Frequencydivisionmultipleaccess (FDMA) and time divisionmultipleaccess (TDMA) are the two major access techniques used to share the available ... the corresponding signal processing techniques at the receiver 1.2 FREQUENCYDIVISION AND TIME DIVISIONMULTIPLEACCESSMultipleaccess schemes are used to allow many mobile users to share simultaneously ... Frequency Available bandwidth Figure 1.3 FDMA scheme in which different users are assigned different frequency bands FREQUENCY DIVISION AND TIME DIVISIONMULTIPLEACCESS User K Time Figure 1.4...
... spread-spectrum multiple- access channels,” IEEE Journal on Selected Areas in Communications, vol 8, no 4, pp 641–649, 1990 [7] P A Hoeher and H Schoeneich, “Interleave -division multipleaccess from ... downlink multipleaccess capacity for Beyond 3G,” IEEE Communications Magazine, vol 43, no 1, pp 61–69, 2005 [10] J C Fricke, H Schoeneich, and P A Hoeher, “An interleavedivision multipleaccess ... values for the carrier frequency and the chip duration 6.2 MMSE channel estimation Let us now turn to MMSE channel estimation Numerical bit error results for frequency- flat and frequency- selective...
... of multiple- access system with multiple antennas at the base station Most previous studies are constrained to either fixed channel condition [11, 12] or ergodic capacity region [13] The space -division ... maximize the sum capacity of a time invariant Gaussian MIMO multiple- access channel The ergodic capacity region for MIMO multiple- access channel with covariance feedback has been studied in [13] ... with multiple antennas,” IEEE Transactions on Information Theory, vol 47, no 4, pp 1273–1289, 2001 [11] B Suard, G Xu, H Liu, and T Kailath, “Uplink channel capacity of space -division- multiple- access...
... differences.The main common technology is orthogonal frequency- divisionmultipleaccess (OFDMA) - There are many good reasons for choosing OFDMA such as multipath handling capability, scalability ... with multiple antenna techniques Nhóm - The focus of this article is on the comparative use of OFDMA in LTE and WiMAX systems USE OF OFDMA IN WIMAX AND LTE Nhóm FRAME STRUCTURE USE OF OFDMA ... uplink uses SCFDMA, which can be viewed asdiscrete Fourier transform (DFT)-spread OFDMA The data is passed through a DFT block before being input to the Nhóm OFDMA module USE OF OFDMA IN WIMAX...
... chi tiết việc sử dụng OFDMA chuẩn WiMAX LTE Cả hai hệ thống tác động nhiều khía cạnh OFDMA bao gồm phân tập tần số, MUD trục tầnsố thời gian Khác biệt khai thác lợi khác OFDMA hệ thống nhấn mạnh ... bố từ trái sang phải khung truyền, thể hình 1a, số lượng sóng mang sử dụng ký tự OFDM giảm Sử dụng phân tập tầnsố Cả WiMAX LTE gặp fading tầnsố có chọn lọc sử dụng băng thông rộng [1, 2] Điều ... Chúng ta so sánh cách sử dụng gắn với khái niệm khác đa tầnsố đa người dùng (MUD) Ví dụ, lợi MUD OFDMA được sử dụng LTE, lợi đa dạng tầnsố triển khai khai thác hầu hết hệ thống WiMAX Ngoài ra,...