HSDPA是3GPP Release 5标准,它能使宽带CDMA(WCDMA)网络速度更快和更智能化.网络运营商基于下面的两个理由会考虑升级到HSDPA:有HSDPA功能的网络能增加容量,而增加容量将会使运营商向更多的用户提供更丰富多彩的服务,从而增加了网络的用户和从每个用户得到更大的收益.本文介绍了HSDPA的市场情况以及所采用的技术和采用HSDPA的好处,同时还详细介绍Freescale 的HSDPA解决方案:支持3.6Mbps(Category 6)的i.300-30 Innovative Convergence™平台和i.300-33平台.
概述:
High Speed Downlink Packet Access (HSDPA) is a Third Generation Partnership Project (3GPP) Release 5 standard that promises to make Wideband CDMA networks faster and smarter. Network operators should consider upgrading to HSDPA for two basic reasons: HSDPA-enabled networks increase capacity, and increased capacity allows operators to offer richer services to more people. For operators who want to realize their investment in 3G networks, HSDPA can increase both the number of users on the network and the amount of revenue per user.
市场:
In order to realize a better return on their investments in 3G licenses, network operators want to get existing and new customers onto 3G networks as quickly as possible. High Speed Downlink Packet Access (HSDPA) is a Third Generation Partnership Project (3GPP™) Release 5 standard that promises to make Wideband CDMA (W-CDMA) networks faster and smarter. With HSDPA, operators can expect to increase capacity, offer richer multimedia services and start getting their money’s worth out of 3G.
There are two overarching reasons why operators want to migrate their customers to 3G: capacity and value-added services. By increasing capacity, operators can accommodate more customers. This leads to increased revenue, a larger customer base to sell services to and greater return on investment.
3G networks are more spectrally efficient than 2G networks, which means that operators can serve more standard voice customers. Transitioning to 3G networks also allows a greater variety of value-added data services such as video telephony, Web browsing and music and video downloads. Many data services that are available today don’t need the promised megabit speeds of HSDPA—although future services will no doubt run at higher speeds. However, operators will need this extra bandwidth both to serve more standard voice customers and to provide higher-bandwidth data services. Without an enhancement such as HSDPA, operators will run out of capacity more quickly.
Revenue Up, Costs Down
Average revenue per user or per unit (ARPU) can benefit from HSDPA. HSDPA increases the efficiency of W-CDMA networks for both voice and data services. The improved voice efficiency frees more of the network for enhanced media services, which in turn offers the opportunity for increased ARPU. That increase in ARPU can help carriers offset the costs of subsidizing new 3G phones for their customers.
HSDPA can help reduce transmission costs and operating expenditures (OPEX) for network operators. It is estimated that delivering a 10 MB file with HSDPA will only be 20 percent of the cost of delivery with W-CDMA.
Some operators can implement HSDPA without high capital expenditure (CAPEX). This depends on the age of the W-CDMA network infrastructure. Older networks may require new hardware for the backplane and channel cards, for example. Most Node Bs installed within the past few years are already HSDPA-capable. The minimal cost to upgrade to HSDPA, balanced with the resulting network benefits, can help improve CAPEX. Terminal availability, rather than network capability, will set the pace for HSDPA uptake.
Operators are already investing heavily in HSDPA, with 117 HSDPA network deployments in 54 countries. Of these, 52 networks have commercially launched services in 35 countries. In five months—between March and August of 2006—the number of commercial networks more than quadrupled.1
The first HSDPA devices have been PCMCIA cards in laptops. However, the market will quickly shift to handheld terminals such as smartphones, entertainment phones and video phones. As over-the-air data transfer speeds increase, emerging standards such as Multimedia Broadcast Multicast Subsystem (MBMS) and IP Multimedia Subsystem (IMS) will enable broader penetration of mobile services such as push-to-share, presence-based services (instant messaging) and mobile television. Figure 1 shows predicted HSDPA handset growth.
技术:
HSDPA introduces advanced methods for modulation, error correction and bandwidth allocation and moves much of the call processing load from the core to the edge of the network. The main goals of HSDPA are efficient packet access, high data rates, reduced round-trip time for a signal between the network and the terminal and backward compatibility with Release 99. The theoretical downlink peak data rate for HSDPA is 14 Mbps, although interference and a user’s location will likely limit real-world data rates to around 10 Mbps.
HSDPA is engineered to help solve performance issues at the W-CDMA network edge. In a “traditional” W-CDMA network, when a user at the edge of a cell is accessing the network at a high data rate, that affects the capacity of the rest of the cell because that one user takes up a lot of the base station bandwidth. A channel that is established at a certain data rate will remain at that data rate continually—so that one user not only takes up a lot of capacity, but could potentially occupy it for some time. With HSDPA, the base station can dynamically change the bandwidth allocation that’s given to one user, based on the cell conditions at any one point. Users with better channel conditions are assigned higher data rates so that they require base station resources for a shorter duration, while users with poor channel conditions at the outer edges of a cell are serviced frequently. This “water-filling” algorithm greatly improves network throughput efficiency.
3GPP Release 5 offers a number of improvements to Release 99. Important features that improve performance and network efficiency include shared channels, fast link adaptation, dynamic scheduling and fast retransmission of packet data.
共享信道:
The High Speed Downlink Shared Channel (HS-DSCH) is, as the name implies, a shared channel. This means that as more users come onto the network, bandwidth is further divided among each user. This is similar to the way that cable modems allocate bandwidth. New HSDPA channels are illustrated in Figure 1.
HSDPA 优势:
Whether you call them 3G, 3.5G or even 4G, there are many technologies that promise high bandwidth and mobility. These include CDMA EV-DO, orthogonal frequency division multiplexing (OFDM), Wi-Fi® and WiMax.
CDMA EV-DO is already available from operators such as Verizon. The highest theoretical data rate for this technology is 2.4 Mbps, compared to HSDPA’s top limit of 14 Mbps. Wi-Fi operates in an unlicensed band, which means that it requires no spectrum licenses. However, it has limited range and is not intended for wide-area network uses. OFDM is a proprietary solution that is targeted for non-cellular bands.
Perhaps one of the strongest alternatives to HSDPA is WiMax. The WiMax theoretical peak data rate is faster than HSDPA, at 70 Mbps per sector, although real data rates are about the same. However, WiMax is not as mobile as HSDPA. WiMax requires new infrastructure and lacks a large enough network for mobility. For true mobility, you need well-engineered handoffs. Handoffs are among the most technologically complex aspects of high-speed mobile services. The general consensus is that HSDPA, being a cellular technology, has the advantage over WiMax in this regard. Table 2 outlines some key technology differences between the two standards.
Table 2. Technology Comparison of WiMAX with 3G4
HSDPA can be thought of as a mobile alternative to broadband asymmetric digital subscriber line (ADSL) and cable modems, although mobile handset processing power doesn’t yet match that of a PC. HSDPA, ADSL and cable have similar real-world throughput rates and provide faster speeds in the uplink than in the downlink.
Freescale 解决方案:
Freescale is one of the early platform vendors to develop an HSDPA solution. The i.300-30 Innovative Convergence™ Platform and the i.300-33 platform are expected to support 3.6 Mbps (Category 6).
Table 3. Planned Availability of Freescale’s HSDPA-Enabled Solutions
Distinctive Combination
Freescale’s combination of the i.300 platform and the Mobile Extreme Convergence (MXC) platform can help OEMs, ODMs and designers to save both time and money. These platforms reduce component count without sacrificing speed or power. The MXC’s single-core modem architecture can significantly reduce design complexity. MXC architecture also frees the ARM11™ processor purely for applications. This architecture allows MXC-enabled devices to take full advantage of the high data rate that HSDPA provides, enabling the richer media and applications that need greater local processing capability.
Because the i.300 and the MXC are the same hardware platform, differentiated by software, manufacturers have a rare choice—to use a traditional architecture or a single-core modem architecture, using the same silicon. This in turn reduces time-to-market and time-to-money.
i.300 Cellular Platform
The i.300 platform is the first dual-mode EDGE Class 12 capable, tri-band W-CDMA/HSDPA, quad-band GSM 3G platform, optimized for open operating systems, with best-in-class integrated UMTS technology.
The Freescale i.300 mobile communications platform is designed to give best-in-class integrated UMTS technology performance and includes an advanced chipset, image and video processing options, an industry-leading development environment and support for rapidly building feature-rich multimedia mobile cellular devices. The i.300 platform chipset includes an industry-leading digital baseband with a dual core modem; an ARM® core applications processor; a 3G ultra-low noise direct-launch modulator integrated circuit (IC); a highly integrated multi-band GSM/GPRS/UMTS receiver IC; a multi-band UMTS/W-CDMA direct conversion receiver IC; a GSM/EDGE/W-CDMA digital transceiver IC; integrated on-chip synthesizers; PA modules that can operate with a single voltage power supply; and a power management and audio interface IC.
Key advantages of the i.300 platform include:
Integrated UMTS feature radio
3.6 Mbps HSDPA Rx / 384 Kbps Tx
EGPRS Class 12
Videoconferencing
Reduced chip count and power consumption RF
Integrated dual-core baseband
Dual core modem protocol stack architecture
Support for real time operating system and open operating systems
MXC Cellular Platform
The MXC platform, the size of a postage stamp, can equip virtually any product—a smartphone, an MP3 player, a handheld DVD player, a digital camera—to become a fully functional smart mobile cellular device. MXC is designed to significantly reduce the materials and development effort required to deliver mid- and high-tier mobile devices. Designed to be inserted in an existing footprint, MXC allows developers to use a single platform to target multiple product designs currently delivered through as many as 300 to 400 components.
Freescale’s MXC architecture represents a radical simplification of the architecture for smart wireless devices while providing a secure environment for content-rich applications. Incorporating more features in a smaller, integrated package reduces complexity, which results in a lower bill-of-materials (BOM) cost than other, more traditional approaches. It can help reduce OEMs’ time-to-market for new converged mobile products by as much as six months and allow software developers to deploy applications across a broad range of devices.
The reduction in complexity and cost is achieved through advances in DSP architecture and communications protocol stack design that enable a single StarCore® DSP core to support the entire communications protocol stack. This breakthrough enables the RISC microcontroller unit, based on the ARM11™ core, to exclusively serve the user application environment. Application processor performance improvement over current discrete application processors is realized by an ARM1136™ core equipped with level 1 and level 2 caches. The L2 cache decouples the CPU from external memory and reduces the need for off-chip memory.
MXC can support open operating systems without a discrete applications processor and without requiring a third processor and a second memory system. For a data call there is no need to turn on the integrated MCU core, which saves power over alternative solutions that must run upper layers of stacks in the MCU core. The MXC has clean separation between the communications engine software (modem core) and the applications software (application core), a simpler software architecture that results in shorter software development times.
Two Architectures, One Chipset
The i.300 platform and the MXC architecture have the same silicon, and are differentiated through software. This provides the flexibility of being able to use one chipset as either a traditional dual-core modem architecture or the MXC single-core architecture.
Using the MXC architecture, OEMS and ODMs will be able to lower their costs for HSDPA-enabled communication subsystems. MXC will enable vendors to provide a smartphone solution at a mid-tier price point. Smartphones were previously restricted to high-tier price points. The reason for this cost savings is that MXC removes one processor and two memory ICs. Freescale estimates that this reduction can save between $10 and $11 US for each chip, and a 20-30% reduction in BOM for handsets (depending on tier).
img src=/manageweb/edit/uploadfile/20070803155438589.gif border=0 align=center>
Figure 2. Block Diagram of Shared MXC and i.300 Architecture
i.300-30 平台特性:
StarCore SC140 DSP @ 208 MHz
ARM11 applications processor @ 400 MHz
Quad-band GSM 850/900/1800/1900 MHz
EDGE GPRS, Class 12 capable
WCDMA tri-band
Data rate WCDMA
384 kbps uplink (UL), 384 kbps downlink (DL)
HSDPA 3.6 Mbps (DL)
Compressed and non-compressed mode
Videoconferencing
Common intermediate format (CIF) video encoder
Integrated Imaging Processing Unit (IPU) video accelerator
Significantly increased processing power to provide gaming, streaming video and videoconferencing. This
comprehensive end-to-end hardware and software solution with full support reduces manufacturer risk and can ultimately save time and money.
i.300-30 平台主要优势:
Extreme hardware integration
Reduced part count and electronic bill of materials (eBOM) costs
From second-generation 3G platform:
25 percent
Reduced IC/module count from 11 to 7
Simplified interfaces
85 cc handset size capable
Simplified development time
Integrated hardware accelerators
Higher performance at longer battery life for users
Reduced system cost
From second-generation platform:
30 percent
Reduced complexity
Proven software, tools and support
Makes certification, interoperability and customization easier, speeding time to market
Protocol stack interoperability testing (IOT) with all major 3G infrastructure suppliers
Reduced current drain
Reduced by >40 percent (200 mA, down from 325 mA in second-generation 3G platform)
Flexible and open platform architecture, both hardware and software
Enables reuse from node to node and across generations
Compelling roadmap with seamless migration path to MXC architecture
Comprehensive HSDPA-enabled solution
Faster download times to consumers without sacrificing battery life
Freescale offers a one-stop-shop with hardware platforms, software, tools and support
Freescale HSDPA 方案
Freescale’s approach to HSDPA technology is especially well-suited to mobile devices such as smartphones, accommodating the cell phone’s evolution from a portable telephone to a mobile computing powerhouse.
Multicall Solutions
Mobile users will work and play in a multicall environment. For example, they might download videos or e-mail attachments, use location-based services or check data across a wireless network—simultaneously, at higher resolutions, while playing a mobile game or participating in a conference call. As the transport user rate increases through HSDPA categories, more complex applications and a richer user experience are possible.
Freescale is one of the early platform vendors to develop a multicall HSDPA solution. The i.300-30 and i.300-33 Innovative Convergence™ platforms and the Mobile Extreme Convergence (MXC) platform currently support up to 3.6 Mbps HSDPA throughput. However, these multicall experiences can tax the applications processing power and battery life of a mobile device. Freescale’s unique Smart Speed power management switch extends battery life even when a user is multitasking. Smart Speed works through a combination of temperature sensing, voltage regulation and on-the-fly frequency adjustment. This means that a Freescale processor can provide performance that is equal to or better than a processor that has a higher clock speed. In an average processor, higher clock speed means greater battery drain—so being able to provide the same performance at lower clock speeds is a power advantage.
External Applications Processor Not Required
On the i.300-30/MXC300-30 platform, the applications processing technology is integrated into the chip with a shared memory system and shared peripherals. This eliminates the need for an external additional applications processor and helps reduce cost. This shared memory approach enables more efficient interprocessor communication, resulting in higher performance, exceptional power management and reduced complexity.
Advanced Receiver Architecture
The i.300-30/MXC300-30 platform has two equalizers to help improve performance, particularly at high data rates. 3GPP has endorsed this architecture for Category 6 and above. The i.300-30 also has diversity support for two receive antennas. This provides a 3 to 6 dB performance improvement. The shared silicon of the i.300 and MXC provides a range of platforms that scale performance through software, from Category 4 to Category 8.
Balancing Software and Hardware
Freescale has implemented HSDPA as a software radio. Flexible hardware is supported by software that can configure the hardware in many different ways. This means that our time-to-market is shorter than it would be with a dedicated hardware solution, because performance can be modified through software. New generations of technology (i.e. modems) can carry applications forward along an evolutionary path. This could reduce time-to-market for consumer products by 6-9 months for each new technology (i.e. 3.5G, 4G, 4.5G, etc.)
The Freescale approach hits an optimal balance of power and cost. Because HSDPA is a recent technology, flexible solutions are required. The most flexible solution is in software—it requires high performance in the DSP, but at higher cost and power consumption. The least flexible solution is hardware, but hardware provides the lowest power and cost. Freescale’s balance is to perform most high-performance operations (chip rate operations) in hardware, and allow software to manage the hardware and perform the symbol rate operations that manage the data from multiple receivers andpower control. This allows flexibility where it is most needed, while not imposing a high and expensive DSP load.
In a conventional architecture, the DSP processor, which does all the software processing for the stack, executes from local on-chip memory. Recent generations of DSPs have some cache on board that allows them to execute instructions from external memory. Freescale’s approach provides caches for instruction and data, and an L2 cache.
For a DSP cache-based architecture, Freescale’s L1 and L2 cache hierarchies on the DSP allows high performance from the DSP when executing code that is stored in external memory. This lowers overall system costs, because the main store for code and data is in external memory. External memory comes in multiple megabytes, so it has the lowest cost per bit, while on-chip memory only come in kilobytes and is expensive to implement.
Managing Performance and Power
Because HSDPA is bursty by nature, peak DSP load varies. This requires high peak performance but in a low power and area implementation. To provide this, Freescale’s solution has a turbo mode in the DSP. This turbo mode increases DSP core frequency (and voltage) to increase DSP performance for the short period of the peak load. To reduce power consumption, the turbo mode uses dynamic voltage and frequency scaling to reduce DSP core frequency and voltage outside of these peaks. This helps reduce power consumption and costs.
来源：中电网 |
