今天通过Wi-Fi实现千兆连接

Content Executive Summary3 Spectrum availability4 Wi-Fi standards evolution6 Detailed analysis: Today's Wi-Fi offers Gigabit speedsthrough 5 GHz and lower 6 GHz bands8 Conclusion18 References19 Authors21 ExecutiveSummary The Digital Decade Policy Programme (DDPP) sets concrete targets and objectives for 2030to guide Europe’s digital transformation. Digital infrastructure is one of the cardinal pointsfocusing on improving and developing mobile and fiber network infrastructures. The goalis to ensure Gigabit connectivity for everyone and achieve high-speed mobile coverage (atleast 5G) everywhere” [1]. The Commission sets the Gigabit connectivity target for fixedbroadband connections delivered to the home [2]. Fixed broadband connectivity is typicallydelivered to households via fiber or fixed wireless access. This is then connected to a Wi-Firouter, which distributes the connection within the home/enterprise. Wi-Fi plays a key rolein maximizing the capacity that reaches the consumer. There are diverging views on how to prevent Wi-Fi from becoming a bottleneck in deliveringGigabit connectivity to consumers. Some request additional spectrum in the upper 6 GHzband [3] while others point to efficiency deficits and argue for more efficient usage of thecurrent spectrum [4]. We have analyzed Wi-Fi performance in an apartment building, considering the mostcommon channel allocation in Europe, namely the 5 GHz and lower 6 GHz bands, fordifferent channel bandwidths, and concluded that: •Speeds significantly higher than 1 Gbps can be achieved today with current Wi-Fitechnology.•The best performance is achieved when combining efficient reuse of the availablechannels with modern Wi-Fi features.•Larger channel bandwidth does not always mean better performance. Throughputincreases, but interference among access points (APs) increases as well. Further emphasis should be put on optimizing operation in dense scenarios withappropriate channel bandwidth and features, rather than overprovisioning of spectrum. Spectrumavailability Historically, Europe has had two spectrum ranges where Wi-Fi technologies can bedeployed: 2.4 GHz, 2400-2483.5 GHz [5] and 5 GHz, 5150-5350 MHz and 5470-5725 MHz[6]. Wi-Fi standardsevolution Wi-Fi is the most common technology being deployed under “license-exempt” authorizationregimes, and its operation in these bands is at the core of the underlying standard, IEEE802.11. In 1997, the first version of the standard [11] supported up to 2 Mb/s throughput usinginfrared or radio transmissions in the 2.4 GHz band. In 1999, IEEE 802.11a rapidlyincorporated the use of the newly available license-exempt 5 GHz band, supportingdata rates of up to 54 Mb/s. Accessing a channel from the begining of the standards isfundamentally based on the principle that a user first senses if someone else is transmittingbefore starting its own transmission. If someone else is transmitting, the user defers. Thismethod is known as carrier-sense multiple access with collision avoidance (CSMA/CA). Thesensing duration is random to avoid simultaneous transmissions by multiple users (knownas collisions). CSMA/CA, by design, is completely distributed, eliminating the need forcentral coordination. It is therefore a good match for the license-exempt spectrum, where nocentral authority or ownership exists. A significant improvement was witnessed in 2009, when the amendment "n" (knownas Wi-Fi 4) introduced multi-antenna transmissions and the doubling of the channelbandwidth to 40 MHz, increasing the maximum raw data rate to 600 Mb/s. At this rate, atransmission of 1000 B takes about 126 μs (14.4μs for the transmission of 4 OFDM symbolscontaining the data, plus 52μs for the preamble, 16μs inter-frame space, and 44μs for theacknowledgment). However, the channel access procedure on average roughly doubles thisduration to 236 μs. This large overhead for every frame significantly results in an achievedthroughput of only 33.4 Mb/s in this example – an efficiency of ~5 percent. Improving thechannel access procedure itself would have introduced fairness problems with the largeinstalled base of legacy users using the spectrum. Hence, the new generation instead addedthe capability to aggregate multiple small frames into one longer transmission. In this way,a single channel access is sufficient to transmit and acknowledge multiple frames, reducingoverheads per frame significantly. This principle continues in the subsequent standard amendment "ac" (known as Wi-Fi5): the raw data rate is increased by quadrupling the maximum channel bandwidth to160 MHz and stuffing more bits into one transmitted symbol, allowing a maximum rawdata rate of 7 Gb/s – resulting in an even lower efficiency for small frames as the channelaccess procedure before the transmission again remained unchanged. As in the previousamendment, this is mitigated by adding more options to aggregate multiple frames perchannel access. For Wi-Fi 5, the strategy is to add multi-use