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The secret hidden in wireless networks: How does CCK break through the 2 Mbit/s limit?
With the rapid development of wireless local area networks (WLAN) today, the demand for data transmission speed is growing day by day. In 1999, Complementary Code Keying (CCK) was introduced as part of the IEEE 802.11b standard to break the 2 Mbit/s data transmission limit in wireless digital networks. CCK not only improves the transmission speed, but also cleverly applies the theory of complementary codes, making this technology an indispensable part of wireless networks.
The introduction of CCK increases the transmission speed to 5.5 Mbit/s and 11 Mbit/s, which not only improves the user experience, but also makes the wireless network more efficient.
CCK’s success comes from its shorter chip sequence. Compared with the early Barker Code, the chip length of CCK is shortened from 11 bits to 8 bits, which means less scalability. However, although CCK can increase data rates compared to Barker codes, it also compromises the transmission range of wireless signals because of its increased sensitivity to narrow-band interference.
"The development of CCK shows that technological progress is often accompanied by trade-offs. We must choose between speed and distance."
There is rich theoretical support behind the design of CCK. Golay, who first discussed complementary codes, pointed out that in a code of length N, the sum of its autocorrelation sequences is zero at all points except zero offset. This characteristic is the basis for CCK to operate effectively. . As a variant of M-ary orthogonal keying, CCK uses polyphase complementary codes. It was developed by Lucent Technologies and Harris Semiconductor in 1998 and works in 802.11 Adopted in the group.
"The application of multiple mutual complement codes enables CCK to achieve high transmission speeds under a relatively small bandwidth."
Specifically, CCK transmits data in symbols of 8 chips per chip in the 802.11b standard. CCK sends data at a rate of 11M chips per second, capable of encoding 4 and 8 bits into symbols in 5.5 Mbit/s and 11 Mbit/s modes respectively. This provides wireless networks with higher data transmission rates and richer application scenarios.
"Through CCK, the data transmission speed of 802.11b exceeded the 2 Mbit/s limit, which was a huge leap in technology at the time."
Because of the similar bandwidth, CCK chose the same preamble and header as the existing 1 Mbit/s and 2 Mbit/s wireless networks during design, effectively promoting interoperability between different devices. In addition, 802.11g standard wireless networks will also use CCK for data modulation when running at 802.11b speed, which further demonstrates the widespread application of CCK technology.
In short, the application of CCK in wireless LAN is not only the result of technological progress, but also an ingenious strategy to solve practical problems. From the initial choice to today's diversified applications, CCK continues to push the boundaries of wireless communication technology. Are there other unexplored avenues for data transfer speeds that can surpass the improvements brought by CCK?
