Comparison Sierra AirCard 771S vs Huawei UMG587

The largest number of devices that can be simultaneously connected to the modem via Wi-Fi (see "Connection").

The presence of this limitation is due to the fact that processing network requests from several devices at once requires a fairly large amount of computing resources, and there are not so many of them in miniature electronics like wireless modems. However, even inexpensive models can support about 5 – 6 devices, which is more than enough for most cases; and in more advanced modems, this number can reach 10.

The greatest distance at which the modem's built-in router is capable of providing communication via the Wi-Fi interface (see "Connection").

It should be taken into account that in fact the range strongly depends on a number of factors that are not related to the main specs of the modem: the presence of interference and obstacles in the signal path, the specs of the Wi-Fi module of the connected device, the battery charge in this device or the modem itself, etc. Therefore, the actual range indicators can be noticeably lower than the claimed ones: for example, when working through a wall, they are noticeably reduced. However, this spec quite clearly describes the overall range of the device, and comparisons of different models on it are quite acceptable.

Also note that it does not always make sense to purchase a device with a maximum range — although a long range provides additional convenience, it requires high transmitter power, which significantly increases the size and price of the modem. Therefore, when choosing, it is worth proceeding primarily from the intended scenarios of use. For example, if you need a 3G connection to access the Internet on the road from your tablet, a range of several metres will be enough. But for installation in a large private house, it makes sense to look for a model with increased effective range.

Data transfer technologies supported by the modem.

— GPRS. The oldest communication technology in use today. It was developed as a standard for GSM cellular networks, allowing data to be transmitted in parallel with voice communications and text messages, as well as charging network access by the amount of data transmitted, and not by connection time (as in the previous CSD standard). At the time of its creation, it was very progressive, but now it is considered completely obsolete and is used only in cases where more advanced standards cannot be used.

— EDGE. A technology created as a modification of the GPRS described above, which would increase the channel throughput and improve communication reliability. Otherwise, this standard is completely similar to GPRS in terms of its main practical features.

— W-CDMA. One of the early third generation ( 3G) communication standards. Used in UMTS networks. One of the main advantages of such networks is the ability to build networks based on the existing GSM infrastructure. Therefore, UMTS, and specifically W-CDMA, is being used by many mobile operators in the early stages of their transition from 2G to 3G.

— HSUPA. Third generation (3G) communication technology, an evolution of W-CDMA described above. The name stands for "Hi...gh-Speed Uplink Packet Access" — high-speed packet data transmission in the "from the subscriber" direction. This, in fact, describes the purpose of this technology: it increases the speed of data transfer from the modem to the base station, which can be useful for some specific tasks — for example, video communications.

— HSDPA. Further, after HSUPA, improvement of the W-CDMA standard (see above). It belongs to third generation (3G) networks, but is considered an “extended” standard, which is why HSUPA-enabled networks can be referred to as 3.5G, 3G+, etc. The name itself — "High-Speed Downlink Packet Access" — translates as "high-speed packet data transmission from the base station to the device."

— HSPA+. Today's most advanced third-generation communication standard based on UMTS networks (W-CDMA). Thanks to a number of improvements, it allows to achieve higher speeds than the options described above, approaching fourth-generation networks in terms of capabilities; therefore, sometimes conventionally referred to as 3.75G.

— WiMAX. Initially, WiMAX was created in two versions — "mobile" and "stationary"; the vast majority of modern cellular modems use the second option. It belongs to the fourth generation standards — 4G (whereas "mobile" was a competitor to 3G technologies, although sometimes it is also referred to as a 4th generation connection for marketing purposes). Some time ago, WiMAX was actively promoted as an alternative to wired broadband Internet connection (in particular, as the best option for areas, where it is difficult to reach the cable). However, now this standard is gradually losing popularity — in particular, in connection with the development and promotion of a more advanced LTE (which also does not have a division into "mobile" and "stationary" varieties).

— LTE (up to 173 Mbps). The fourth generation cellular communication standard, the most popular 4G technology today — in particular, due to the fact that it is a further development of W-CDMA/UMTS and can be implemented by improving existing networks (both UMTS and CDMA2000). Another reason for the popularity is the same convenience for both stationary and mobile equipment. On the other hand, when choosing a modem of this standard, you should keep in mind that LTE bands and channels may differ in different countries, so the support of this technology does not guarantee compatibility with a particular network. It should also be taken into account that in some countries LTE networks are only at the deployment stage, and in some they are not available at all.

— EV-DO (Rev.A). EV-DO is a third-generation (3G) data transmission technology used in CDMA mobile networks (not to be confused with W-CDMA, built on another basic standard — UMTS). Note that in some countries this type of 3G network became widespread much earlier than W-CDMA and its modifications, and for a number of technical reasons it is mainly used for data transmission — that is, for the operation of 3G modems. As for Rev.A, this is the second and most common version of the EV-DO standard.

— EV-DO (Rev. B). The third version of EV-DO technology, the development and improvement of Rev.A; see above for details. Here we note that this standard is also often used as a 3G data connection; its coverage area is not as extensive as the previous version, but still covers most major cities and their surroundings. It is also worth considering that in order to use all the features of Rev.B, you need a modem that supports this version, and not all modern EV-DO devices can do this.

When evaluating the capabilities of a modem, note that the speed values given for each technology are the maximum, which in fact is achievable only under perfect conditions. The actual values of the speed, usually, are lower than the potential ones; they may depend both on the specs of the network, signal strength and other technical issues, and on the policy of the operator and the conditions of a particular tariff.

The capacity of the battery installed in the modem with the corresponding type of power supply (see below).

The higher the capacity, the longer the battery is able to work without recharging, all other things being equal. However, note that the situation of "other things being equal" is almost not found in modern wireless modems. First, different data transmission technologies (see above) have different power consumption; secondly, even models supporting the same standards can differ in power consumption (and battery life) due to design differences. Therefore, this indicator in most cases is purely reference information, and even very similar models can only be compared approximately. When choosing, it is worth focusing primarily on the claimed specs of the battery life (see below).