csma cd carrier sense multiple access with collision detection

... 13 2.2.1CDMA (Code Division Multiple Access) .13 2.2. 2CSMA/ CD (Carrier Sense Multiple Access with Collision Detection) : .13 2.2. 3CSMA/ CA (Carrier Sense Multiple Access with Collision ... xuất môi trường 1.3.1 Đa truy xuất cảm nhận sóng mang có phát đụng độ CSMA/ CD( Carrier Sense Multiple- Access With Collision Detection) Giao thức đường dây đa truy cập cho phép nhiều trạm thâm nhập ... lớn hơn, khiến máy thu hoạt động truyền đến từ nút cần dự tính 2.2.2 CSMA/ CD (Carrier Sense Multiple Access with Collision Detection) : Đa truy xuất cảm nhận sóng mang với thăm dò đụng độ Trong...

Ngày tải lên: 28/03/2014, 13:20

... and WiMAX standards use several common technologies with subtle differences.The main common technology is orthogonal frequency-division multiple access (OFDMA) - There are many good reasons for ... 12 adjacent subcarriers are grouped as a unit in the subcarriers in an OFDM symbol frequency axis, and OFDM symbols (or OFDM symbols in A slot is formed by combining a subchannel with different ... (Partially Used Sub -Carrier) , subchannels - Within an OFDM symbol, no FD USE OF OFDMA IN WIMAX AND LTE USE OF MULTIUSER DIVERSITY - In WiMAX, the BAMC organize groups of contiguous subcarriers - Each...

Ngày tải lên: 24/07/2015, 22:26

... lý đoạn đầu Bằng cách sử dụng DL-MAP, thông điệp xa đường xuống kênh mô tả (DCD) (định kỳ) đường lên kênh mô tả (UCD) phải đọc với UL-MAP để bắt đầu trình nhập mạng Tất thông điệp điều khiển ... xuống đường truyền lên DL-MAP UL-MAP Loại MCS sử dụng phần khác khung cho đường xuống đường lên DCD UCD (Tạ Văn Bách) Network Entry PDCCH PDCC Trong WiMax, preamble truyền phần đầu tất khung, thời ... vào tính hiệu lượng [2] Trong WiMAX, phương pháp phân kênh bắt buộc gọi PUSC ( Partially Used SubCarrier ), kênh hình thành cách nhóm 24 sóng mang trình bày phần khác quang phổ Lựa chọn giả ngẫu...

Ngày tải lên: 24/07/2015, 22:27

... keying (QPSK) Sophisticated multiple access technology like frequency division multiple access (FDMA), time division multiple access (TDMA) and code division multiple access (CDMA) also gained prominent ... era, CDMA rose in prominence as it became the multiple access technology of choice for the two most popular 3G system standards: Wideband CDMA (W-CDMA) and CDMA2000 Compared to FDMA/TDMA, CDMA ... division multiple access (OFDMA) scheme [26] with discrete fourier transform (DFT) precoding and equidistant frequency mapping [17, 24, 25, 27] or a code division multiple access (CDMA) scheme with...

Ngày tải lên: 08/09/2015, 18:24

... and CDMA, OFDM-CDMA can be categorized as Multicarrier CDMA (MC-CDMA), Multicarrier DS-CDMA and Multitone CDMA [8] C OFDM-FDMA OFDM-FDMA is generally termed as Orthogonal Frequency Division Multiple ... of multiple access schemes to share resources among different users Typical OFDM-based multiple access techniques include Time Division Multiple Access (OFDM-TDMA), Code Division Multiple Access ... Hybrid allocation Subcarriers … … … Time Interleaved allocation (c) OFDM-FDMA with different subcarrier allocation schemes Fig.1.4: Typical multiple access techniques used with OFDM A number of...

Ngày tải lên: 14/09/2015, 14:03

... depicted cases with multiple users, that is, there is virtually no loss in power efficiency compared to the case without MAI We therefore obtain a quasiorthogonal multiple access without the need ... 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 multiple access from ... downlink multiple access 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 multiple access...

Ngày tải lên: 22/06/2014, 23:20

... 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] In ... to the base station and model this as a multiple- access system All mobile are equipped with single antenna element, and the base station is equipped with multiple receive antenna elements to exploit ... space-division -multiple- access schemes,” IEEE Transactions on Information Theory, vol 44, no 4, pp 1468– 1476, 1998 [12] W Yu, W Rhee, and J Cioffi, “Optimal power control in multiple access fading channels with multiple...

Ngày tải lên: 23/06/2014, 01:20

... attempting to determine if the channel is in use Carrier sense multiple access (CSMA) and carrier sense multiple access/ collision avoidance (CSMA/ CA) are both contention-based Random wait Random ... based on the CSMA/ CA + ACK protocol for unicast frames and the CSMA/ CD (carrier sense multiple access/ collision detection) protocol for broadcast frames It also deploys a virtual carrier sense mechanism ... practice 1.2.2 Carrier Sense Multiple Access and Carrier Sense Multiple Access/ Collision Avoidance The main drawback to ALOHA and Slotted ALOHA is that transmitters blindly transmit without attempting...

Ngày tải lên: 27/06/2014, 14:20

Ngày tải lên: 25/07/2014, 09:39

... Access Control 15 1.2.1 ALOHA .16 1.2.2 Carrier Sense Multiple Access and Carrier Sense Multiple Access/ Collision ... DIVISION MULTIPLE ACCESS (CDMA) Multiple access techniques Conflict-free Contention-based Random access Collision resolution ALOHA, CSMA, CSMA/ CA, RTS/CTS, etc TREE, WINDOW, etc TDMA, CDMA, FDMA, ... CDMA and more widely understood orthogonal access techniques such as time division multiple access and frequency division multiple access Additionally, random access schemes such as carrier sense...

Ngày tải lên: 07/08/2014, 21:20

... attempting to determine if the channel is in use Carrier sense multiple access (CSMA) and carrier sense multiple access/ collision avoidance (CSMA/ CA) are both contention-based Random wait Random ... based on the CSMA/ CA + ACK protocol for unicast frames and the CSMA/ CD (carrier sense multiple access/ collision detection) protocol for broadcast frames It also deploys a virtual carrier sense mechanism ... practice 1.2.2 Carrier Sense Multiple Access and Carrier Sense Multiple Access/ Collision Avoidance The main drawback to ALOHA and Slotted ALOHA is that transmitters blindly transmit without attempting...

Ngày tải lên: 07/08/2014, 21:20

... MULTIPLE ACCESS (CDMA) FIGURE 2.4: Comparison of original/despread signal and spread signal spectra for DS/SS with square pulses 2.2.2 Multiple Access The DS/SS technique can be expanded to multiple ... DIVISION MULTIPLE ACCESS Now that we have described the main types of CDMA, let us now turn to the performance of CDMA systems This discussion will start with DS-CDMA—specifically, with the performance ... TECHNIQUES FOR CODE DIVISION MULTIPLE ACCESS 45 structure described is optimal only in the absence of multiple access interference Time hopping can be thought of as DS/SS with tertiary (three-valued)...

Ngày tải lên: 07/08/2014, 21:20

... statistics 2.8 MULTIPLE ACCESS PERFORMANCE OF FREQUENCY-HOPPED CODE DIVISION MULTIPLE ACCESS Although the emphasis of this chapter is DS-CDMA, we would like to examine the performance of FH-CDMA systems ... 56 September 28, 2006 15:54 CODE DIVISION MULTIPLE ACCESS (CDMA) 0.9 0.8 B B B B B B = = = = = = CW tone 25 MHz 100 MHz 225 MHz 400 MHz 500 MHz 0.7 0.6 CDF P1: IML/FFX MOBK023-02 0.5 0.4 0.3 0.2 ... additional channel estimation, which can be substantial 2.6 MULTIPLE ACCESS PERFORMANCE OF DIRECT SEQUENCE CODE DIVISION MULTIPLE ACCESS The previous section examined the performance of a single...

Ngày tải lên: 07/08/2014, 21:20

... 2006 15:55 CODE DIVISION MULTIPLE ACCESS (CDMA) 3.1.4 Statistical Multiplexing The final fundamental CDMA concept that we will discuss in this section is termed statistical multiplexing, which is ... Comparison of Multiple Access Capacity To see the advantage of CDMA over other multiple access techniques, let us first pursue a firstorder comparison of the capacity of FDMA, TDMA, and CDMA based ... DIVISION MULTIPLE ACCESS SYSTEM OVERVIEW Now that the key concepts of CDMA have been introduced, a typical cellular CDMA system can be described Here we are specifically interested in DS-CDMA systems,...

Ngày tải lên: 07/08/2014, 21:20

... capacity determined by the CDMA Development Group, or CDG, (the commercial consortium of CDMA cellular providers), we find that this estimate is optimisitic Specifically, the CDG quotes a capacity of ... simultaneously but randomly access the system This effect was discussed in Chapter and impacts all types of cellular systems regardless of the multiple access technique In cellular CDMA systems, there ... 1.25 ms in IS-95 and cdma2000 and half that length in UMTS P1: IML/FFX MOBK023-03 P2: IML MOBK023-Buehrer.cls 102 September 28, 2006 15:55 CODE DIVISION MULTIPLE ACCESS (CDMA) AWGN channel 1.5...

Ngày tải lên: 07/08/2014, 21:20

... protocols are termed the multiple access collision avoidance/common-transmitter (MACA/C-T) and the multiple access collision avoidance/receiver-transmitter (MACA/R-T) protocols [46] CSMA can also be ... contentionbased multiple access Such multiple access techniques are useful in packet radio networks that cannot afford the overhead or infrastructure associated with scheduled access techniques ... MOBK023-Buehrer.cls 114 September 28, 2006 15:55 CODE DIVISION MULTIPLE ACCESS (CDMA) Node Node de Co Node #2 Comm on co de Secondary collision Primary collision Node de Co #4 de on co m m Node Co Node Node...

Ngày tải lên: 07/08/2014, 21:20

... 127 CHAPTER Multiuser Detection As discussed in previous chapters, the conventional matched filter receiver treats multiple access interference (MAI), which is inherent in CDMA, as if it were additive ... limiting factor in the capacity of CDMA systems As a result, capacities for single-cell CDMA systems can be substantially lower than those for orthogonal multiple access techniques such as TDMA or ... IML/FFX MOBK023-05 P2: IML MOBK023-Buehrer.cls 132 September 28, 2006 15:56 CODE DIVISION MULTIPLE ACCESS (CDMA) CDMA receivers Single user Matched filter Multiuser Adaptive filters Optimal (MLSE)...

Ngày tải lên: 07/08/2014, 21:20

... IML/FFX MOBK023-05 P2: IML MOBK023-Buehrer.cls 148 September 28, 2006 15:56 CODE DIVISION MULTIPLE ACCESS (CDMA) b Matched filter User - Σ+ - Matched filter User b1 - + Σ - Matched filter User b2 ... biased after cancellation with the bias increasing with system loading One method of alleviating this problem is to multiply the estimate by a partial cancellation factor with a value in the range ... IML/FFX MOBK023-05 P2: IML MOBK023-Buehrer.cls 150 September 28, 2006 15:56 CODE DIVISION MULTIPLE ACCESS (CDMA) Mathematically, we can represent the bit decisions for an S-stage parallel cancellation...

Ngày tải lên: 07/08/2014, 21:20

... 17:14 CODE DIVISION MULTIPLE ACCESS (CDMA) [14] F A Tobagi and L Kleinrock, “Packet switching in radio channels: Part III—Polling and (dynamic) split-channel reservation multiple access, ” IEEE Transactions ... Societies, pp 776–783, March 1999 [47] G Qiang, Z Liu, S Ishihara, and T Mizuno, “CDMA-based carrier sense multiple access protocol for wireless LAN,” in Proceedings of the 2001 IEEE Vehicular Technology ... Kleinrock, “Packet switching in radio channels: Part II—The hidden terminal problem in carrier sense multiple- access and the busy-tone solution,” IEEE Transactions on Communications, vol 23, pp...

Ngày tải lên: 07/08/2014, 21:20

... tính đột phá mặt công nghệ phát triển sở hệ thống 3G W-CDMA HSDPA có tốc độ truyền tải liệu lên tối đa gấp lần so với sử dụng công nghệ WCDMA Về mặt lý thuyết, HSDPA đạt tốc độ truyền tải liệu ... liệu dạng video nhạc HSDPA phát triển dựa công nghệ W-CDMA, sử dụng phương pháp chuyển đổi mã hóa liệu khác Nó tạo kênh truyền liệu bên W-CDMA gọi HS-DSCH (High Speed Downlink Shared Channel), ... ích chất lượng dung lượng HSDPA sở có dung lượng tế bào cao gấp lần WCDMA HSDPA cải tiến có dung lượng tế bào cao gấp lần WCDMA Hiệu suất trải phổ HSDPA cải tiến bị giới hạn 1bit/s/Hz/cell.Mức...

Ngày tải lên: 02/06/2015, 17:26