SSID

SSID(service set identifier )a name used to identify the particular 802.11 Wireless LANs to which a user wants to attach. A client device will receive broadcast messages from all access point within range advertising their SSIDs, and can choose one to connect to based on pre-configuration, or by displaying a list of SSIDs in range and asking the user to select one. กลุ่มของอักขระที่มีขนาดความยาวไม่เกิน 32 ตัวอักษร ใช้อ้างอิง service set ของเครือข่าย wireless LANs

PoE Technology

Super G technology

Atheros Super G technology operates in two modes to increase bandwidth. The base mode uses standards-based data compression, large frames and bursting features to deliver real-world network throughput in excess of 40 Mbps for typical data files, an increase of up to two times over traditional 802.11g networks. The new Dynamic Turbo extends the feature set of Super G products by adding a capability that automatically detects and adapts to nearby Super G, 802.11g, and 802.11b products. Super G products employ a number of technologies to achieve performance gains over standard 802.11g products. The primary (and most problematic from a standards standpoint) is channel bonding. Super G products can bond two 20-MHz channels together. This 40-MHz footprint is centered on channel 6. This can cause adjacent channel interference on the only other two nonoverlapping channels in the 2.4-GHz spectrum, channels 1 and 11. That means the introduction of a Super G access point in close proximity to an existing 802.11g network can dramatically decrease the performance of the 802.11g network. Another technology used by Super G is packet bursting, which lets the AP and client card send more packets on each transmission, thereby making better use of air time by reducing the number of interpacket intervals. In addition, Super G's fast packets technology packs more data into each packet.
Source: Pcmag.com, bestbuy.com, nerfwear.com, wi-planet.com, atheros.com

Wireless LAN Requirement

-Throughput: medium access control protocol ให้ capacity ปานกลางถึงสูงสุด
- Number of node: สนับสนุนมากกว่า 100 โหนดผ่านหลายๆเซล - Connection to backbone LAN: สำหรับ mobile terminal และ ac hoc wireless wireless network
- Service area: การครอบคลุมพื้นที่ของเซลมีเส้นผ่าศูนย์กลาง100-300เมตร
- Battery power consumption: ต้องการแบตเตอรี่ที่ใช้งานได้นาน
MAC protocol ใช้ monitor การใช้งานควบคุมโดยสถานีฐาน
-Transmission robustness and security: เป็นการเชื่อมต่อ Wireless LAN ในสภาพที่มีสัญญาณรบกวนและกำหนดระดับสัญญาณที่ใช้งานได้อย่างปลอดภัย - Collocated network operation: มีการอินเตอรเฟอร์เรนท์ระหว่าง Wireless LAN ที่มาตรฐานต่างกันโดยใช้ MAC algorithum - License-free operation: ผู้ใช้สามารถซื้ออุปกรณ์ Wireless LAN ที่มี source license ตามความถี่ใช้งาน
- Handoff/roaming: จะใช้ MAC protocol ในการเปลี่ยนเซล - Dynamic configulation:MAC addess และ network management ใช้ addition relocation แบบอัตโนมัติ

Graphs for Data Network

IEEE 802.11a, b and g

As of this writing, the IEEE 802.11 standard has evolved into 3 complementary recommendations, called A, B and G.

802.11A
IEEE 802.11a devices use a different radio technology from 802.11b and operate in the 5 GHz bands. IEEE 802.11a therefore is a supplement to the basic IEEE 802.11 standard.
Although the IEEE 802.11a standard operates in a different unlicensed radio band, it shares the same proven Medium Access Controller (MAC) protocol as Wi-Fi. In more technical terms, IEEE 802.11a standardizes a different physical layer (PHY). Since products conforming to the IEEE 802.11a standard will operate in different radio bands, they will not be interoperable with Wi-Fi radios, which follow the b-recommendation (see below).

802.11B
802.11b contains some further definitions of the physical layer, and provides for interoperability of Wi-Fi™ WLAN products. Wi-Fi products operate in the worldwide 2.4 GHz Industry, Science, and Medicine (ISM) band.


802.11G
As of this writing, the IEEE 802.11g recommendation has been accepted, but not implemented. An example, using Intersilดs idea OFDM (Orthogonal Frequency Division Multiplexing) is a compulsory part of IEEE 802.11g and provides for transmission speeds up to 54 Mbit/sec. It would be compatible with WiFi. It also supports CCK (Complementary Code Keying) in order to be compatible with existing radio units that adhere to IEEE 802.11b.
The CCK transmission mode, also used by WiFi, uses one single carrier, while OFDM is a new technique, just entering the WLAN-market. It can be used both at 2.4 and 5 GHz carrier frequencies.
OFDM is quite interesting. Different blocks of the same data transmission is divided between sub-carriers, thus enhancing receptivity also in environment having strong signal distorsion. It also has greater transmission capacity than CCK.

The 802.11 Physical Layer

The IEEE 802 standards committee formed the 802.11 Wireless Local Area Networks Standards Working Group in 1990. The 802.11 working group took on the task of developing a global standard for radio equipment and networks operating in the 2.4GHz unlicensed frequency band for data rates of 1 and 2 Mbps. The standard does not specify technology or implementation but simply specifications for the physical layer and Media Access Control (MAC) layer.
The Physical Layer in any network defines the modulation and signaling characteristics for the transmission of data. At the physical layer, two RF transmission methods and one infrared are defined. Operation of the WLAN in unlicensed RF bands requires the spread of spectrum modulation to meet the requirements for operation in most countries.
The 2 RF transmission modes specified in the 802.11 standard are:

1.Frequency Hopping Spread Spectrum (FHSS)

2.and Direct Sequence Spread Spectrum (DSSS).

Both architectures are defined for operation in the 2.4GHz frequency band, typically occupying the 83 MHz of bandwidth from 2.400 GHz to 2.483 GHz. Differential BPSK (DBPSK) and DQPSK is the modulation for the direct sequence. Frequency hopping uses 2-4 level Gaussian FSK as the modulation signaling method. The radiated RF power at the antenna is set by the rules governed by FCC part 15 for operation in the United States. Antenna gain is also limited to 6 dBi maximum. The radiated power is limited to 1W for the United States, 10mW per 1Mhz in Europe and 10mW for Japan. There are different frequencies approved for use in Japan, United States and Europe.

แนวโน้มความต้องการของตลาดทางด้านอินเทอร์เน็ตความเร็วสูง ปี 2008

1.Communications for All ประชาชนทุกระดับชั้นสามารถใช้บริการบรอดแบนด์ได้ในราคาถูก
2. Broadband Everywhere สามารถใช้บริการได้ทุกพื้นที่เพราะเป็นคลื่นสัญญาณแตกต่างจากในอดีตที่จำเป็นต้องลากสายเข้าไป (ฟิกซ์ไลน์)
3.Personalization & Communities เป็นลักษณะของการแชร์ข้อมูลระหว่างกัน และ การร่วมแบ่งข้อมูล ที่ตนเองและกลุ่มของตนเองสนใจ