Pokémon Black Version and White Version include a feature called Random Matchup, where players can battle others from anywhere in the world via Wi-Fi.
In Random Matchup Rating Mode, each player has a rating that goes up or down depending on which other players the player played against and the outcome of each battle. (There is also Free Mode, where a player’s rating is not used, regardless of the battle’s outcome.)
The Global Battle Union
Rating information can be viewed via the Global Battle Union (GBU), a feature of the Pokémon Global Link Web site.
The GBU is divided into seasons. A player is included in the GBU ranking by finishing, in a single GBU season, 10 or more Rating Mode battles that end in a win or a loss. Battles that end because players are disconnected, and battles that end in a draw, are not counted in rating or ranking.
After each GBU season, the top 100 players in the overall ranking get a special avatar. Starting in season 5 of the GBU, ratings, wins, and losses are reset at the start of the season.
Each player’s rating starts at 1500 and goes up or down after each battle, depending on its outcome. According to this page (see Asrialys’s post from October 20), the GBU appears to use the Elo rating system to score players. That post also says that the K-Value is probably 32. This information seems likely to be the case.
About the Elo System
The Elo system uses a rating and a K-Value to score players. When two players finish a match, the winner gains more points (up to the K-Value) if his or her rating is lower than the loser’s, and less points if it’s higher, and the loser loses that many points. How many points? Here’s the formula:
If the higher rated player loses: Points = K-Value * (1 / (1+10Rating Difference / 400))
If the higher rated player wins: Points = K-Value – K-Value * (1 / (1+10Rating Difference / 400))
If both players have the same rating, the winner gains half the K-Value, and the loser loses the same amount.
The Pokémon Global Link holds “competitions” from time to time. Before the competition starts, players register up to six Pokémon that they will use in that competition. The registration period can be up to seven days. The competition itself lasts five days. During the competition, players try to get the highest rating they can by battling as much as they want. (Competition ratings are tracked separately from GBU ratings.)
All battles started within the competition period are counted, even those that end after the period is over.
In Random Matchup Rating Mode, a player is matched with another player with a similar rating. Rating Mode requires the Pokémon Global Link to be online, however.
In Random Matchup Free Mode, a player is matched with any other available player.
Each season of the GBU lasts about 3 months. The seasons began on the launch of the Pokémon Global Link for North America and Europe, which was April 13, 2011.
The GBU updates rankings weekly, presumably during the weekly maintenance periods every Tuesday when the Pokémon Global Link goes offline. (Ratings appear to be updated in shorter intervals.) Ratings, wins, and losses were carried over from season 1 to 2, from season 2 to 3, and from season 3 to 4. From season 5 (March 29, 2012) on, this doesn’t happen anymore. The GBU tracks ratings for each battle mode (Double, Launcher), Rotation, Single, and Triple, as well as an overall rating for all battle modes (source).
In some earlier competitions, such as the “2012 International Challenge”, a player is not counted in competition rankings if that player:
- Doesn’t finish 10 or more Rating Mode battles that end in a win or a loss during the competition; or
- Has a rating of 1600 or greater and the player’s disconnection rate is 10 or more points higher than the average rate among all players; or
- Has a rating of less than 1600 and the player’s disconnection rate is 20 or more points higher than the average rate among all players.
A player’s disconnection rate is equal to (number of disconnections) / (wins + losses + disconnections), counting all battles in the competition. (Source: Pokémon Global Link page for the 2012 International Challenge).
A possible reason why players must win or lose 10 battles to be ranked is that new players can have widely ranging skill levels, so unless a player has played several games, the GBU can’t be confident of the player’s skill level. The Random Matchup matchmaking system probably takes this fact into account.
Dark Void is not allowed in Random Matchup Free Mode as of December 27, 2011, and in Rating Mode as of December 28, 2011. Chatot is not allowed in Random Matchup.
In Random Matchups, a Pokémon’s nickname is not used.